Birmingham Hip Resurfacing—Designer Surgeon’s Technique

RECONSTRUCTION 2023, Jan, 16 | 12:00 am

Birmingham Hip Resurfacing—Designer Surgeon’s Technique

Introduction

In the management of end-stage hip arthritis in young patients, the primary goal of hip resurfacing is to provide a conservative alternative until an age at which conventional total hip arthroplasty (THA) would be more suitable. If painfree hip function can be restored and maintained in the face of the high activity demands of young people, without in the process jeopardizing the chances of a future conversion to a THA, hip resurfacing can be considered to be a useful conservative option. The aim of the implantation procedure is to achieve good fixation of the components on to good quality bone in the femoral head and acetabulum, in a position that is conducive to low wear by avoiding edge loading of components and allowing the potential for in vivo fluid film lubrication. We describe the posterior approach for Birmingham Hip Resurfacing (BHR) in this chapter.

Implant—The Birmingham Hip Resurfacing (BHR)

The BHR has a hydroxyapatite-coated, porous, uncemented acetabular component and a cemented femoral component, both made of as cast high-carbon cobalt-chrome alloy. Since neither component is subjected to postcasting heat treatment they retain their wear resistance. The femoral heads and cups are supplied in 2 mm increments, with cup sizes ranging from 44 to 66 mm. There is a cup thickness choice of 3 or 4 mm and Dysplasia cups with a provision for supplementary screw fixation. On the fixation surface the cup has castin beads integral to the cup substance and consequently, at very low risk of dislodgement in vivo, a phenomenon observed with sintered beads and plasma spray in some instances. Independent analysis has shown that the surface roughness of the BHR components is in the region of 0.03 μm, mean deviation from roundness in the range of 0.9 μm.1 Radial clearance varies with the bearing diameter. The metallurgy and design features are based on the forensic analysis of several successful first generation McKee-Farrar, Ring and Stanmore metal on metal (MoM) devices with a track record of several decades in clinical use.

Indications

Resurfacing is an ideal solution for young active patients with end-stage arthritis, provided the femoral head bone quality is reasonable.2 In the Western world, primary osteoarthritis is the most common indication.3,4 In Eastern series,5 femoral head osteonecrosis (ON) predominates, although our experience constrains us to employ a different approach in ON, as discussed in a subsequent chapter.

Total Hip Arthroplasty

Some conditions pose a particular challenge to stemmed THA, and are therefore better treated with a hip resurfacing. With a THA it is difficult to reconstruct a large femoral offset or fit a stem in a deformed femoral shaft or a very wide femoral canal. Osteopetrosis also poses problems for stem implantation and therefore a resurfacing offers another solution.

Contraindications

Active infection and severe vascular deficiency are unsuitable for any arthroplasty including hip resurfacing. Since resurfacings employ MoM bearings, patients with proven hypersensitivity to metal or those in renal failure are unsuitable.

Patients with poor quality bone in the femoral head and neck due to any reason including osteopenia, severe cystic change or extensive ON, are at high-risk of failure with a resurfacing. Patients with Crowe grade IV dysplasia, malignant tumors in and around the hip, and severe limb length discrepancy especially, if it arises from outside the hip are best treated with a THA. Older inactive patients are better treated with a THA, due to the possibility of poor bone quality. However physiological age is more relevant than chronology alone. Patient activities and co-morbidities must also be taken into account. Provided patients are chosen carefully,

we find that the medium term results in older patients are as good as in the young.

Preoperative Planning

A well-centred AP pelvis radiograph is required in all cases and a lateral view is also essential, in particular, in those who have abnormal morphology or had previous surgery. The goal of the planning process is to ensure the presence of bone of adequate quality in the regions of interest, and achieve placement whereby the two components lie in a mutually coaxial plane at an angle of 40 degrees to the long axis of the body in the erect coronal plane and a combined anteversion (sum of femoral neck and cup anteversions) of no more than 45 degrees in the transverse plane.

FEMORAL TEMPLATING

We continue to have access to conventional radiographs which makes templating easy. However, many surgeons have to manage with digital radiographs which can be entirely satisfactory if used with magnification markers and good software. However, if used without magnification markers and appropriate software, digital radiographs can lead to major errors in sizing and femoral component alignment.

Using conventional radiographs, we first choose an appropriate size of template, one which clears the femoral neck and obtains good circumferential peripheral femoral head support. Next the ideal position for the stem is established. Varus position leaves exposed cancellous bone laterally and extreme valgus leads to notching of the lateral neck. A position between these extremes is ideal (Figs 14.1A to C).

ACETABULAR TEMPLATING

Acetabular positioning is similar to any other cementless THA shell and, in general, an inclination of 40 degree and a combined cup and femoral anteversion of 45 degrees are desirable. However, greater care is necessary in resurfacing, to fine tune the cup position relative to proximal femoral morphology. In the presence of socket insufficiency, a dysplasia cup with supplementary screws6 may be required (Fig. 14.2) to achieve proper placement, bypassing and reconstructing the insufficiency.

In women femoral anteversion also needs careful preoperative assessment. If there is a suspicion that this is excessive, CT scan assessment is necessary. A small increase in anteversion can be compensated by placing the cup in a less anteverted position. If femoral anteversion is greater than 45 degrees it is preferable to perform a THA. Alternatively

Birmingham Hip Resurfacing—Designer Surgeon’s Technique

Figures 14.1A to C: Templating (A) The young age, high activity level and large femoral offset (as seen on his left hip) make this 43-year-old male more suitable for a resurfacing than a THA. External rotation hip deformity hides the true offset on the right. (B) The template that clears the femoral neck and obtains good peripheral femoral head support is chosen. Placing an appropriately sized template in the desired position, a measurement is taken from the long axis of the femoral component to the tip of the lesser trochanter. This measurement will help obtain optimal varus-valgus alignment at surgery.

Figure 14.2: Hip Dysplasia, Crowe Grade I socket insufficiency in this 51-year-female required correction with a dysplasia BHR cup with supplementary screw fixation and bone graft reconstruction of the socket. The cup is placed in a closed position (35° inclination) in order to compensate for the more vertical coxa valga femoral neck

resurfacing can be combined with a corrective femoral derotation osteotomy in a very young patient. This is a much more extensive procedure and a longer, slower rehabilitation7 and should therefore be discussed at the original consultation.

Finally, a cardinal principle in conservative hip arthroplasty is to remember that it is unacceptable to overream the acetabulum in order to go conservative on the femoral side. Acetabulum takes precedence over the femur in terms of bone conservation. In most cases, femoral anatomy allows the surgeon the freedom to use the smallest cup needed for the given natural acetabular dimensions, without the concern that the matching femoral component would notch the neck. Therefore the natural socket dimensions dictate the resurfacing sizes used. In some of those rare instances such as coxa magna from post-Perthes’ disease or developmental dysplasia, where femoral anatomy for a resurfacing would constrain us to use a larger acetabulum, it is preferable to resort to a more invasive procedure such as the BMHR or even a THA rather than unnecessarily over-ream the acetabulum. During surgery, acetabular preparation is performed first so that the femoral head is not prepared to an incorrect size.

Total Hip Arthroplasty

Anesthesia

We use a low thoracic hypotensive epidural anesthesia (HEA) supplemented by general anesthesia maintaining the patient at just sufficient depth so that, the patient stays asleep during the procedure. This combination offers the benefits of a relatively bloodless operative field, reduced blood loss and reduced nausea associated with the general anesthetic medications. It allows early mobilization and a reduced incidence of venous thromboembolism. We do not use anticaogaulants for thromboprophylaxis but employ a multimodal regime which includes HEA, antiplatelet medication, early mobilization, compression stockings and pneumatic calf pumps and routinely perform diagnostic ultrasonography on both lower limbs and pelvis of all patients the third to fifth postoperative day to detect subclinical deep vein thrombosis (DVT).

We discourage long-term NSAID usage in general because it has been shown that they cause femoral head damage in the presence of osteoarthritis of the hip. We advise disconti-nuation of all nonsteroidal anti-inflammatory drugs (NSAIDs) at least three weeks before the operation in order to allow the coagulation profile to return to normal. Aspirin and anticoagulant medications are also discontinued before surgery in consultation with the treating physicians. In inflammatory arthritis we do recognize that NSAIDs play a beneficial therapeutic role.

Surgery

A detailed description of the technique has been published earlier8-10 and is recommended reading in order to follow the finer nuances in the technique. The instrumentation used is shown in Figures 14.3 to 14.5. We use a short posterior approach but do not hesitate to extend it for better exposure where necessary (Figs 14.6A to C).

EXPOSURE

Starting at a point which is around 5 cm distal to the tip of the greater trochanter at its posterior border proceeding obliquely at an angle of around 20 degrees to the long axis, we extend the incision posterosuperiorly and anteroinferiorly as shown in Figures 14.3A to C. This is more posterior than a traditional incision and allows good access to the acetabulum and the lesser trochanter while ensuring that the dislocated femoral head is delivered into the center of the wound. Skin and subcutaneous tissue are incised along this line. The incision lies in the same direction as the fibers of gluteus maximus. After achieving adequate hemostasis, the fibers of G max are separated along the same line and the division is extended distally into the fascia lata (Fig. 14.7).

Birmingham Hip Resurfacing—Designer Surgeon’s Technique

Figure 14.3: BHR cup instrumentation

Cup reamers
Reamer handles
Cup trials
Cup alignment guide
Offset cup introducer
Hammer for cup impaction
Cable cutter for cup impactor cap cables

Figure 14.4: BHR femoral instrumentation 1
1. Measuring guide (to site the guide pin on intertrochanteric crest)
2. Guide pin
3. Femoral alignment jig (Short arm jig)
4. Anti-notch device
5. Anti-notch spacers
6. Guide pin relocator
7. Arthroscopic cannula (Vent)
8. Cannulated drill for femoral head
9. Taper drills (3)
10. Peripheral femoral head cutters (Barrel reamers)
11. Face cutters to resect and plane femoral head summit

Total Hip Arthroplasty

Figure 14.5: BHR femoral instrumentation 2

Guide bars
Intraoperative templates
Handle for templates
Napkin rings (optional)
Chamfer cutters
Guide bar extractor
Wrobleski drill
Scrub brush
Femoral impactor/introducer

Figures 14.6A to C: Skin incision. (A) In the lateral position, the pelvis is stabilized with a bolster against the pubis anteriorly and a lumbar support posteriorly. The traditional posterolateral approach is marked here only for comparison. (B) We recommend a posterior approach which is less extensive than the traditional approach. A point approximately 5 cm distal to the tip of the greater trochanter is marked on the posterior border of the trochanter. (C) A 10 to 15 cm incision proceeds obliquely posterosuperiorly from this point. The distal end is extended in the same direction for 2 or 3 cms

14

Birmingham Hip Resurfacing—Designer Surgeon’s Technique

Figure 14.7: Division of gluteus maximus and fascia lata. Fibers of the gluteus maximus (G max) are separated along their length in the line of the skin incision extending distally for about two centimeters into the fascia lata in the line of its longitudinal fibers. The under surface of gluteus maximus is separated from the underlying trochanteric bursa. The sciatic nerve is palpated posteriorly and a Charnley retractor is then positioned ensuring the sciatic nerve is protected

Figures 14.8A and B: Division of capsule and short external rotators. (A) The gluteus medius (G med) and minimus (G min) are retracted using a pin retractor inserted above the superior acetabular edge as shown, making sure it is sufficiently superior not to transfix the femoral head. (B) Starting at the insertion of the piriformis tendon the external rotators are divided along with the attached capsule close to the posterosuperior edge of the trochanter. This incision is carried proximally along the superior border of piriformis to the edge of the acetabulum and distally through the obturator/gemelli and quadratus femoris. A cuff of muscle is left attached to the posterior femur for subsequent closure or else it may be necessary to drill holes in the back of the greater trochanter later

The proximal 1 to 2 cm of the G max insertion on the linea aspera is divided to prevent sciatic nerve compression when the limb is rotated. The trochanteric bursa is then divided along the posterior margin of the greater trochanter (GT) and from the posterior margin of the gluteus medius (G med).

Proceeding deeper, the edge of G med is retracted forwards using a large Langenbeck retractor to expose the layer consisting of the gluteus minimus (G min), Piriformis, obturator internus/gemelli and the quadratus femoris (Figs 14.8A and B). All the above except the

14

Total Hip Arthroplasty

Figure 14.9: Capsular incisions. The piriformis, obturator internus/gemelli and the quadratus femoris are divided along with the capsule to expose the hip. A radial cut is made through the posteroinferior capsule and a pin retractor inserted into the ischium 1.0 to 1.5 cm away from the acetabular edge

Figures 14.10A and B: Dislocating the hip and delivering the femoral head. The hip is dislocated by drawing the thigh and leg into a position of flexion and internal rotation (A). The knee is then brought back to the mid-line longitudinal axis of the patient (B) so that the hip is positioned in full extension. The assistant then forcibly internally rotates the limb delivering the femoral head up into the wound and allowing the surgeon to gain access to the anterior aspect of the hip capsule

glutei are divided along with the capsule to expose the hip. It is critical to identify and divide the piriformis tendon from the trochanter. Otherwise it makes further steps very difficult. The next step is to detach the origin of the fibers of the gluteus minimus from the underlying superior edge of the acetabulum and the ilium with electrocautery or a heavy muller scissors. This step reduces the risk of Gluteus minimus fibers getting torn and leading to heterotopic ossification.

A radial cut through the posteroinferior capsule (Fig. 14.9) allows a lip of the posterior capsule along with the quadratus femoris to be retracted posteriorly exposing the posterior wall of the acetabulum. The superior capsule is also divided before the hip can be dislocated by drawing the thigh and leg into a position of flexion and internal rotation (Figs 14.10A and B). The upper border of the psoas tendon is then identified and spared. Using a Muller scissors the anterior hip capsule is divided half way between the edge of the acetabulum and the femur, starting at its inferior end and proceeding superior (Fig. 14.11A). The assistant then flexes the hip to 45 degrees and internally rotates the hip and the superior part of the anterior

14

Figures 14.11A and B: (A) Division of the anterior capsule. (B) Complete presentation of the femoral head into the wound following the division of the anterior capsule

Birmingham Hip Resurfacing—Designer Surgeon’s Technique

Figures 14.12A and B: Femoral Osteophytes (A) Trimming of femoral head osteophytes from all around (B) Care must taken to preserve soft tissues on the femoral neck

capsule is divided starting at its superior end and proceeding inferiorly to connect with the previous incision in the inferior aspect. When the leg is in this rotated position, the femoral vessels are a safe distance away (Fig. 14.11B).

Osteophytes must be trimmed from all around from the femoral head including the anterosuperior femoral neck osteophyte at the head-neck junction (Figs 14.12A and B). Care must be taken not to tear soft tissue off the femoral neck.

After clearing osteophytes, intraoperative templating is performed. First the smallest head-neck template size that will clear the femoral neck is identified. The template is then applied to the femoral head and the maximum size that will obtain peripheral head support is also determined. These measurements give the smallest femoral component that does not damage the femoral neck and the largest that will obtain peripheral support indicating the range of matching acetabular components that can be used in the particular patient. The smallest cup in this range which obtains the best fix in the acetabulum is the required cup size (Figs 14.13A and B).

A large blunt-tip hook is placed around the femoral neck and anterosuperior soft tissues are divided to create a space for displacing the femoral head and allow access to the acetabulum (Figs 14.14A and B).

14

Total Hip Arthroplasty

Figures 14.13A and B: Intraoperative templating. (A) Smallest head-neck template size which will clear the femoral neck, and (B) maximum size that will obtain peripheral head support are determined

Figures 14.14A and B: Gaining more access to the acetabulum. A large blunt-tip hook is placed around the femoral neck and the second assistant displaces the femoral head and neck in an anterosuperior direction. The anterosuperior acetabular labrum is then grasped with heavy Kocher forceps and excised giving clear sight of the anterosuperior acetabular edge. A Muller scissors is then used to snip around the anterosuperior acetabular edge resting the tips of these scissors on bone in order to create a space into which the femoral head can be displaced to allow access to the acetabulum

Two further acetabular retractors are placed around the socket one inferiorly below the transverse ligament and the tear-drop which is hooked onto the Charnley frame and another over the front of the acetabulum to be held by the second assistant. Now we have 360 degree access to the acetabulum. This wide exposure of the acetabulum is critical to a successful resurfacing (Figs 14.15A and B).

ACETABULAR IMPLANTATION

The labrum and ligamentum teres remnant are excised. Osteophytes in the posterior wall are removed and the normal horseshoe shape of the fovea is re-created. All the soft tissue from

14

Figures 14.15A and B: A Hohmann retractor with a sturdy tip is then driven into the ilium at least 1 cm away from the acetabular edge. The surgeon then takes the patient’s foot in one hand and the Hohmann retractor in the other, and slowly the femoral head is prolapsed under the abductor muscles by externally rotating the leg. The leg is then allowed to adopt its own comfortable position just off the front edge of the operating table on a sterile covered pillow placed between the operating table and an instrument trolley. In that position, the leg allows the femoral head to stay displaced over the anterosuperior acetabulum

Birmingham Hip Resurfacing—Designer Surgeon’s Technique

Figure 14.16: In order to avoid severe over-reaming, it is advisable NOT to ream the acetabulum until cancellous bone is exposed all around. There must be a mixture of cancellous and cortical bone exposed. However, all overlying articular cartilage or soft tissue needs to be excised and curetted out.

the floor and the transverse ligament are excised and acetabular vessels deep to the transverse ligament are coagulated.

Acetabular reaming is started with a small reamer (generally size 43 or 45) steadily deepening until the true acetabular floor is reached checking frequently to ensure the floor is not over-run. In primary osteoarthritis it is often necessary to bias the reamer in an anterosuperior direction where arthritic wear has occurred, so that when final reaming is reached satisfactory support for the component is present (Fig. 14.16). In hip dysplasia, the opposite bias is necessary because of anterosuperior deficiency. Reaming is continued with progressively larger reamers (2 mm increments each) until the last three which are increased in 1 mm increments.

A 2 mm press-fit is the norm with the BHR. This can be achieved by under-reaming 2 mm. In very small women 1 mm under-ream is preferable and in the presence of hard bone 1 mm under-ream is preferred and in very soft bone 3 mm under-ream is preferred. A trial acetabular cup is then placed in the acetabulum and impacted. The diameter of the trial

14

Total Hip Arthroplasty

Figure 14.17: The acetabular cup on the introducer is positioned in the correct alignment, i.e. with the anti-rotation flanges lying against the ischium and the pubis

cup is 1 mm smaller than the definitive implant. The trial cup should seat firmly in the acetabulum but it should be possible to move it with moderate force. If the trial cup needs to be impacted very hard during positioning, or if it is very difficult to change position, the socket needs further reaming in 1 mm increments until the desired fix is achieved. Socket cysts are curetted and bone grafted with reamings.

Any soft tissue projecting towards the acetabulum is retracted and the cup is positioned and impacted with a heavy mallet. During impaction the handle has a tendency to ride high into abduction. This must be resisted and an active attempt must be made to hold the handle down in order to reduce cup inclination. When a change in impaction tone denotes that the cup has reached the acetabular floor, it will also be noticeable that the implant fails to advance with subsequent impaction.

Inclination and anteversion are checked with an external alignment guide (Figs 14.18A and B) aiming for 40 degrees of inclination and 20 degrees of anteversion. The native acetabular wall is in approximately 55 degrees inclination and if its edges are used to line up the cup edges, the component inclination will be too high (Figs 14.18A and B). Cup position

Figures 14.18A and B: The external alignment guide used to check cup anteversion (A) and inclination (B)

14

Birmingham Hip Resurfacing—Designer Surgeon’s Technique

Figure 14.19: When the cup is aligned well in both planes, and when it is securely fixed, the introducer is removed, the polyethylene cap is retracted and the position is checked all around to ensure the position is as planned and that there is sufficient anterior bony coverage

Figure 14.20: If the edges of the native acetabular walls are used as a reference to line up the component edges, the cup inclination will be too high. A conscious attempt must be made to close the cup by holding the impactor down during impaction. Anteriorly however all the metal of the cup has to be buried under bone in order to prevent painful psoas irritation

is also checked internally (Fig. 14.19) to ensure that the metal is not uncovered anteriorly in order to prevent psoas irritation and pain later.

If on inspection (Fig. 14.19) the position is not satisfactory, then the cables should not be cut. The introducer is reattached and component position changed either by removing it and reinserting it, or by manual pressure in the desired direction and re-impaction. When the position is satisfactory, then the cables are cut and the cap removed. If the cables are cut before this is achieved, it is difficult to re-position the cup. There is a disposable extractor kit available, if necessary but it is much easier and preferable not to cut the wires before satisfactory positioning is ensured. Protruding osteophytes are then trimmed off around the acetabular component to prevent impingement.

Anteriorly it is imperative not to expose bare metal (Fig. 14.20) in order to prevent the psoas tendon rubbing against the cup edge. Hence there should be at least 2 mm of bone protruding beyond the metal edge of the cup. We inject a mixture of Ropivacaine, Adrenaline and Ketorolac into the raw tissues around the acetabulum for postoperative analgesia and that completes acetabular component insertion.

14

FEMORAL IMPLANTATION

Total Hip Arthroplasty

During femoral preparation for a resurfacing it is very important to ensure the blood supply of the femoral head is not jeopardized. To that end, the soft tissue of the femoral neck should be respected and preserved during all stages; and a vent must be used in the proximal femur in order to reduce small vessel embolization in the femoral head and neck. Furthermore notching of the femoral neck should be avoided at all costs.

The femoral component should be centred on the femoral neck rather than on the center of the femoral head and neither varus position nor an extreme valgus position are desirable. It is also necessary to maximize anterosuperior head-neck offset in order to minimize impingement. As the assistant internally rotates the leg once again, the femoral head comes up into the center of the wound.

The first step (Fig. 14.21) is to mark the position for the attachment of the short femoral jig on the intertrochanteric crest by measuring the distance from the lesser trochanter previously decided on radiographic templating. A pin is then inserted at this point through the short jig aperture ensuring that the guide pin is at right angles to the intertrochanteric crest. The correct position of the guide pin determines accurate varus-valgus alignment.

When a satisfactory lateral plane alignment has been achieved then the hinge is locked. The correct lateral plane alignment of the jig (Fig. 14.22) ensures the guide wire goes down the center of the femoral neck when viewed in the lateral plane. Correct varus-valgus and lateral plane alignments are thus achieved. The next step is to determine the ideal entry point for the guide wire.

The stylus is now rotated around the femoral neck to identify the ideal entry point. The best point will allow the stylus tip to pass comfortably around the femoral neck without touching the neck. When it is applied on the femoral head the stylus stays in contact with the periphery of the femoral head all the way round. The anterosuperior head-neck offset should be maximized within the constraints of the earlier two requirements.

When the ideal entry point has been located, then the guide wire is inserted. After this the short arm jig and the guide pin are removed and a final check of the guide wire performed by reinserting the cannulated bar and passing the stylus tip around. If unsatisfactory, the guide wire can still be removed and repositioned at this stage. The guide wire relocator comes in handy to fine tune the position of the entry point. The next step is to drill through the lesser trochanter into the femoral canal and insert an arthroscopic irrigation cannula through the drill hole. This is attached by thick walled tubing to a separate suction unit to

Figure 14.21: Entry point for guide wire. The radiographic measurement (lesser trochanter to the long axis of the femoral component template), is transferred on to the intertrochanteric crest by marking the entry point for the attachment of the femoral jig using a diathermy tip

14

Birmingham Hip Resurfacing—Designer Surgeon’s Technique

Figure 14.22: When the guide pin has been inserted then the cannulated bar in the jig is placed against the femoral head and the stylus is moved down the inferior surface of the femoral neck. The hinge is now released in the arm of the jig and the instrument is gripped firmly. The first assistant then places a pick up forceps on the front and back of the femoral neck to facilitate an estimation of the mid lateral axis

constantly decompress the bone and prevent embolization of local vessels and reduce systemic embolization.

Before starting femoral reaming, the soft tissues need to be protected from the debris by spreading two wet swabs over the wound around the femoral neck (Figs 14.23A and B). Overdrilling the guide wire allows a guide bar to be placed and its position is checked using the stylus in order to exclude the possibility of guide wire deviation within the bone. If its position is satisfactory, then the anti-notch device is applied in order to prevent notching of the femoral neck during the process of reaming (Fig. 14.24A). The device is advanced down the superior femoral neck, until it reaches a point beyond which the risk of notching appears imminent. This allows us to determine the appropriate thickness of anti-notch spacer necessary.

Figures 14.23A and B: The guidewire should be in line with the center of the femoral neck and often appears to lie eccentric on the arthritic femoral head. An arthroscopic irrigation cannula through a drill hole in the lesser trochanter acts as a vent to decompress the proximal femur

14

Total Hip Arthroplasty

Figures 14.24A and B: The anti-notch device (A-ND) is placed on the guide bar and advanced till it touches the first point on the superior femoral neck. This allows us to find the appropriate anti-notch spacer (Sp) that will ensure notching is prevented when the peripheral femoral head cutter (PFHC) is used for femoral reaming

Figures 14.25A and B: (A) At the end of reaming the rim is separated from all around the femoral head except often at its posteroinferior aspect where it remains loosely attached. This is easily detached with a periosteal elevator and (B) the soft tissue attachments are divided by sharp dissection with a blade

The spacer is placed over the guide bar on the top of the femoral head. For additional protection the head-neck template can also be used around the femoral neck to prevent notching (Fig. 14.24B). The peripheral femoral head cutter is then applied on the ream setting and advanced until it reaches the anti-notch spacer. The cutter is slowly advanced using progressively thinner spacers until further advancement risks femoral notching. Reaming is then stopped and the weakly attached inferior and posteroinferior peripheral femoral head bone is gently cracked off with a periosteal elevator (Fig. 14.25A).

Sometimes too much intact bone medially may need the use of a reciprocator saw. The attached soft tissue is carefully released by sharp dissection (Fig. 14.25B). Protruding osteophytes around the femoral head-neck junction are removed with rongeurs.

Either a face cutter instrument or a napkin ring and reciprocating saw can be used to resect the summit of the femoral head (Fig. 14.26). In both cases resection point should be

14

Birmingham Hip Resurfacing—Designer Surgeon’s Technique

Figure 14.26: The medial femoral head-neck junction is the reference point for placement of the napkin ring. The apex of the femoral head can be divided with a reciprocating saw as shown in this figure

Figure 14.27: The anterosuperior part of the femoral head (arrows) in an osteoarthritic hip appears deficient before the chamfer cut is made. After chamfer cut step is completed, the deficiency disappears. The cutter can be used in the drill or ream setting

Figures 14.28A and B: Cement key holes on the surface of the femoral head (A) and taper drill (B) to be used in the central hole

determined with reference to the medial head neck junction. A final check is made with the head-neck template to ensure that the correct resection level has been achieved. If further resection is needed the face cutter is useful. In primary osteoarthritis at this stage there appears to be an anterosuperior defect on the femoral head.

The chamfer cutter is then used over the guide bar until this instrument is fully seated (Fig. 14.27). Its internal stop safeguards against over-resection. Generally by the end of the chamfer cut, the anterosuperior defect would have disappeared. Key holes (Fig. 14.28A) are then drilled into the femoral head using a suitable drill. A curette is used to clear any sub-

14

surface cysts and remove all loose bone and soft tissue. Cysts at the head neck junction and on the walls of the femoral head are risk factors for failure. If these are extensive we choose the Birmingham Mid Head Resection Prosthesis (BMHR, Smith and Nephew Orthopedics, Warwick, UK).

Total Hip Arthroplasty

A taper drill is used to widen the central hole in the femoral head and neck into a taper (Fig. 14.28B). Because the femoral stem of the BHR is tapered, it can cause incomplete seating of the femoral component if the hole remains a parallel sided hole, particularly when the bone is sclerotic. Pulse lavage and a brush are used to open up the cancellous network and optimize cement mircointerlock. The guide bar is reinserted and the head-neck template reapplied to mark the point on the femoral head-neck junction to which the femoral component must be advanced during implantation. The correct size and the color code on the package label of the femoral component are checked by the surgeon and matched against the color code on the cup package. In addition the laser marked size on the femoral component stem is also checked by the surgeon.

Antibiotic simplex cement is mixed in a mixing bowl with a spatula (Figs 14.29A and B). Vacuum mixing must be avoided because it will increase cement viscosity early. When the cement goes fluid it should be drawn up into a syringe and transferred into the component. The component is then slowly rotated so that the cement reaches all the fixation surfaces. One minute after mixing, the femoral component is inserted onto the femur. The femoral head pusher is applied on the component with steady firm pressure and tapping lightly with a hammer.

The femoral component advances with each tap. It is advisable not to continue the impaction rapidly and relentlessly, as this will overwhelm the suction vent and marrow begins to ooze out through the femoral neck cortex causing embolization of small vessels in the femoral head and neck with potential for devascularization. After every two or three impactions a few seconds break is good to allow vent decompression. When the edge of the femoral head reaches the mark on the head-neck junction, then the component is fully seated and no further impaction should be done (Fig. 14.30). Excess cement is curetted out and the protecting swabs are carefully removed taking with them bone debris and cement debris. Remaining osteophytes especially at the head-neck junction are removed while taking care not to damage femoral neck soft tissue. Saline soaked swabs are applied to the femoral neck flushing out displaced fat and marrow through the cannula, which is then removed.

A Langenbeck type retractor is used to retract soft tissue from the superior aspect of the socket. Thorough pulse lavage of the hip ensures that all bone, cement and debris is washed out. The cup is then filled with saline and the hip is reduced while applying traction on the leg in order to prevent scratching the femoral component on the edge of the cup. During reduction, as fluid rushes out from the cup, it displaces all soft tissue out of the acetabulum

Figures 14.29A and B: Antibiotic simplex cement is used without vacuum mixing (A) and is transferred into the component with a syringe, filling the component one-third full

(B). Implantation is done exactly one minute after mixing began

14

Birmingham Hip Resurfacing—Designer Surgeon’s Technique

Figure 14.30: Using the head-neck template, its distal end is marked on the medial head-neck junction (inset). This marks the point to which the femoral head should be advanced. During impaction when the femoral component reaches the mark, the component is fully seated and no further impaction should be done

preventing entrapment between the head and cup. This is then checked visually and by palpation. Leg length, stability and range of movement are checked and it is ensured that there is no impingement through the full range of movement. If correct principles are followed, leg length and stability are not common problems. Impingement can occur in external rotation and extension in hip dysplasia. Increased femoral neck anteversion leads to bony impingement between the lesser trochanter region and the ischium. Impingement can also occur in slipped upper femoral epiphysis morphology in flexion and internal rotation, when the anterior femoral head-neck offset has not been adequately restored. The second dose of Ropivacaine, Adrenalin and Ketorolac are then injected into the posterior capsule, external rotators and posterior soft tissue on the femur. The abductors and gluteus maximus muscle fibers are also infiltrated through their exposed surfaces.

CLOSURE

We use two suction drains, one in the hip and the other deep to the G max—fascia lata layer. The external rotators and the capsule are repaired using continuous 0 looped PDS using mattress type locking and applying loose approximation only. A tight suture line would cause muscle edge necrosis and breakdown of the suture line. The first stitch, applied at the junctional area between the abductors and the greater trochanter, fixes the piriformis tendon and the superior capsule securely. If a good soft tissue cuff has not been left on the posterior aspect of the trochanter, drill holes may be necessary to get satisfactory closure. After about three to four centimetres, the capsule can no longer be picked up and closure of quadratus femoris continues. Inferiorly the edges of the divided tendon of G max are approximated as well. The suture line is then turned proximally and the greater trochanter bursa is approximated with a running suture. The next layer (fascia lata and the fibers of G max) are approximated using looped 0 nylon running sutures taking care not to strangulate the muscle fibers. We use a Miller’s hitch and bury the knot at the end. The subcutaneous tissues along with the fascia covering the G max muscle are repaired with Vicryl and skin closure is performed with skin clips.

14

Alternative                   Techniques

Resurfacing can be performed through different types of approaches and it has been demonstrated that both the anterolateral and posterior approaches offer equally good longterm implant survivorship and hip function when performed well. It has also been shown that femoral head viability is well-preserved through the posterior approach in spite of having to sacrifice the medical circumflex femoral artery (MCFA) during the procedure, as long as the soft tissue envelope of the femoral neck is preserved and adequate precautions (such as medullary venting) are taken to prevent embolization of the vasculature in the femoral head and neck. The trochanteric flip approach, which was specifically developed for the benefit of MCFA preservation, has been found to suffer from a higher risk-benefit ratio in terms of creating major trochanteric problems without any demonstrable benefit from MCFA preservation. Its usage has therefore been given up in several centers. A few centers continue to use the anterior approach as well for hip resurfacing. In our practice although we started with the anterolateral approach, we soon found the posterior approach more beneficial in terms of excellent visualization for implantation and minimal soft tissue disruption. The near absence of limp or other gait problems following this approach allows our patients to declare that they have forgotten about their hips and carry on with life as normal.

Total Hip Arthroplasty

Tips      and      Pearls/      Cautions

Preoperative planning. When the planning is for a young woman there should be a high index of suspicion to look for dysplasia. It is important to make an assessment of socket insufficiency and femoral neck anteversion clinically and radiographically. If there is suspicion of marked version abnormality, it is advisable to assess socket and femoral anteversion with a multislice CT scan. If femoral anteversion is less than 45 degrees it is possible to implant the socket in reduced anteversion so that the combined femoro acetabular anteversion remains 45 degrees. If femoral anteversion is greater than 45 degrees, resurfacing will need to be combined with subtrochanteric derotation osteotomy or it is necessary to perform a THA. These possibilities should be discussed with the patient during the outpatient consultation because the surgical procedure and the rehabilitation regimen with these are different to those of a straight-forward resurfacing and the patient should be given an opportunity to make an informed decision.

During exposure, when identifying the external rotators (Figs 14.8A and B), it is important to accurately identify the piriformis tendon and be conscious of its anatomic variations. Unless this tendon is divided from its attachment to the trochanter it makes further steps very difficult by preventing adequate rotation. The piriformis insertion may be blended with the obturator internus, which poses no problem since it will then be detached. In others the piriformis blends with the posterior fibers of gluteus medius. If this is not recognized and the connection between piriformis and gluteus medius fibers not divided, one may be led to mistake the obturator internus for the piriformis tendon and leave the piriformis attached to the trochanter. This must be avoided.

Before the hip is dislocated it must be ensured that the femoral head is not trapped by protruding socket osteophytes. Especially in the presence of protrusio acetabulae, if the femoral head is trapped by the presence of an osteophyte forceful rotation during dislocation can lead to fracture of the femoral shaft. The osteophyte needs to be excised before dislocation. While releasing the anterior capsule (Figs 14.11A and B) it is important to ensure that the psoas tendon is not divided. Division of the psoas in young, active patients results in difficulty in

getting the foot on and off car pedals and in actively flexing the hip beyond 90 degrees.

During the step when the capsule, muscle and reflected head of rectus femoris are being detached from the anterosuperior edge of the acetabulum with a Muller scissors (Figs 14.14A and B), it is important to bear in mind that the femoral vessels are close to the acetabulum in

14

this region. Great care must be taken to avoid injury. The tips of the scissors must never leave contact with the bone as cutting into the soft tissues could jeopardize the femoral vessels.

Birmingham Hip Resurfacing—Designer Surgeon’s Technique

It is important to remove femoral head and neck osteophytes before intraoperative templating of the femoral side (Figs 14.12A and B). Left-over osteophytes can force the surgeon into using a femoral component that is too large which in turn implies excessive reaming of the acetabulum.

The Hohmann retractor (Figs 14.15A and B) which is used to retract the anterior capsule and femoral head out of the way of the acetabulum must be sturdy. If during the process of usage it fractures, it is almost impossible to retrieve the tip.

During cup implantation (Figs 14.17 to 14.19), allowing the cup to be guided by the margins of the native acetabulum can result in the cup being left in an open and anteverted position. This can be a recipe for edge loading and accelerated wear with all its attendant problems including elevated systemic metal ion levels and pseudotumors.

During implantation of the femoral component (Fig. 14.30) sometimes the edge of the femoral head does not reach the templated point marked out on the medial head neck junction with the template. This incomplete seating of the femoral head may occur as a result of the summit resection being at an angle, wrong cement being used or vacuum mixing of cement, implantation being delayed more than one minute after cement mixing; or the mark being made in the wrong place on the medial head-neck junction. Excessive force used in an attempt to advance the stalled femoral head has in the experience of some led to intra-operative fracture of the femoral neck or head.

The correct size and the color code on the package label of the femoral component must be checked by the scrub nurse and the surgeon and matched against the color code on the cup package. In addition the laser marked size on the components are also checked by the surgeon. Packaging errors have occurred in the past and should be avoided at all costs.

Leg length assessments are important in DDH and in femoral conditions such as Perthes’ disease. If significant leg length adjustments are necessary in excess of what can be achieved by way of restoring the hip center and improved postoperative pelvic mobility, hip resurfacing may not be the right procedure for the patient. In routine osteoarthritic cases it is very difficult to inadvertently lengthen the leg with the resurfacing procedure. If lengthening of the leg following a resurfacing has occurred, it could be due to a major error on either the acetabular or femoral side of the procedure or both.

During closure while repairing the capsule and external rotators and the superior end of the insertion of the fascia lata, the sciatic nerve lies close by inferiorly and it is advisable to expose or feel where it lies, in order to prevent picking it up inadvertently.

After the patient is transferred from the operating table to the bed an X-ray is taken in the recovery room when the patient is wide awake to ensure that dislocation has not occurred in moving from the operating room table.

Postoperative                 Management

We do not use anticaogaulants for thromboprophylaxis but employ a multimodal regime which includes HEA, antiplatelet medication, early mobilization, compression stockings and pneumatic calf pumps and routinely perform diagnostic ultrasonography of all patients on the third to fifth postoperative day to detect deep vein thrombosis (DVT).

We take all the necessary precautions to try and reduce infection including perioperative intravenous antibiotics continued for 24 postoperative hours, antibiotic cement fixation of the femoral component, operating in a clean air laminar flow enclosure and Charnley body exhaust suit. Our antibiotic prophylaxis consists of Cefuroxime 1.5 g started before the operation and continued for three doses after the procedure. The patient is allowed out of bed full weight bearing (WB) with a Zimmer frame on the first postoperative day. From the second day onwards, a pair of elbow crutches are used with full WB mobilization, for a

14

period of four weeks followed by a walking stick in the contralateral hand for another four weeks. We perform an ultrasongraphic assessment for DVT on the 3rd to 5th postoperative day, by which time patients are independent in their mobilization, transfers and on stairs and are ready to go home. In bed they are allowed to roll on to their opposite side with a pillow between their knees. Clips are removed on the 12 to 14th day. If significant bone graft reconstruction of the socket has been performed we allow partial weight bearing only with two elbow crutches during the first four weeks followed by another four weeks of full WB with elbow crutches. Only during the first 6 weeks we advise patients not to sit on a very low chair, bend their hips acutely or cross their legs. They do not need to use a raised toilet seat. All patients are encouraged to perform breast stroke swimming and work out with graduated stretching and strengthening exercises from six weeks on. Impact loading activities are delayed until one year after the procedure.

Complications

General complications with the BHR are no different to those with other arthroplasty devices. Without the use of anticoagulants, our current incidence of below knee DVT is 1.83% with the BHRs and 2.1% with THRs. Only 1.8% of the BHRs and 5.2% of THAs needed a blood transfusion. The reasons for revision of BHRs are shown in Figure 14.31.

Total Hip Arthroplasty

Results

With revision of either component for any reason as the end point, the survivorship in our series of BHRs including all ages and diagnoses, with a minimum follow-up of 6 months is 99% at 5 years, 98% at 10 years and 96% at 13 years (Fig. 14.32). The survivorship in men

is 99%, 98% and 97% and in women 98%, 96% and 93% at 5, 10 and 13 years respectively. Men in all ages and women 60 years and above have a 13-year survivorship of 97% while in women under 60 it is 92%. The lower survivorship in young women is related to the fact that DDH is a common primary pathology in young women. In young and active patients

Figure 14.31: Showing reasons for revision in the 3195 BHRs

14

Birmingham Hip Resurfacing—Designer Surgeon’s Technique

Figure 14.32: Survivorship of BHR over 13 years for all ages and diagnoses

with osteoarthritis who have been described as the supreme challenge to total hip arthroplasty survivorship, the survivorship of BHRs is 98% at 13 years.

Illustrative Case

The radiographic series of a patient with primary osteoarthritis treated with a Birmingham Hip Resurfacing. His preoperative radiograph shows characteristic features of osteoarthritis with superolateral joint space loss, large floor osteophyte, reasonable femoral head bone quality and minor lateral subluxation of hip. Postoperative view shows good restoration of hip biomechanics. Ten years after his original operation he continues to experience symptom-free hip function (Fig. 14.33).

Figure 14.33

14

References
1. Heisel C, Kleinhans JA, Menge M, Kretzer JP. Ten different hip resurfacing systems: biomechanical analysis of design and material properties. Int Orthop 2009;33(4):939-43.
2. Daniel J, Pynsent PB, McMinn DJ. Metal-on-metal resurfacing of the hip in patients under the age of 55 years with osteoarthritis. JBJS [Br] 2004;86:177-84.
  
  Total Hip Arthroplasty
3. Daniel J, McBryde C, Pradhan C, Ziaee H. Results of Birmingham hip resurfacing in different diagnoses. In McMinn DJ (Ed). Modern Hip Resurfacing. London, Springer 2009.pp.357-70.
4. McMinn DJ, Daniel J, Ziaee H, Pradhan C. Indications and results of hip resurfacing. Int Orthop 2010 Nov 16. [Epub ahead of print]. PMID: 21079954.
5. Bose VC, Baruah BD. Resurfacing arthroplasty of the hip for avascular necrosis of the femoral head: a minimum follow-up of four years. J Bone Joint Surg Br 2010;92(7):922-8.
6. McMinn DJ, Daniel J, Ziaee H, Pradhan C. Results of the Birmingham Hip Resurfacing dysplasia component in severe acetabular insufficiency: a six- to 9.6-year follow-up. J Bone Joint Surg Br 2008;90(6):715-23.
7. Daniel J, Pradhan C, Ziaee H, McMinn DJ. Management of Complex Anatomy. In McMinn DJ (Ed). Modern Hip Resurfacing. London, Springer 2009.pp.333-48.
8. McMinn DJ, Patient positioning and Exposure. In McMinn DJ (ed). Modern Hip Resurfacing. London, Springer, 2009.pp.189-202. Modern Hip Resurfacing. London, Springer 2009.pp.189-300.
9. McMinn DJ, Acetabular preparation and insertion of the standard Birmingham Hip Resurfacing cup. In McMinn DJ (Ed). Modern Hip Resurfacing. London, Springer 223-264, 2009. Modern Hip Resurfacing. London, Springer 2009.pp.223-64.
10. McMinn DJ, Implantation of the femoral component of the Birmingham Hip Resurfacing. In McMinn DJ (Ed). Modern Hip Resurfacing. London, Springer 223-264, 2009. Modern Hip Resurfacing. London, Springer 2009.pp.265-300.

Birmingham Hip Resurfacing—Designer Surgeon’s Technique

Search in this site