Anterior Minimally Invasive Total Hip Replacement (AMIS®)

Dr Glase is Australia’s most experienced surgeon in the AMIS® technique and since 2007 has successfully performed over 3000 cases. He is one of a small number of surgeons who will routinely replace both hips during the one surgical procedure (bilateral). He has Australia’s largest series of bilateral AMIS® procedures with over 200 cases. He is widely regarded as the pioneer of the AMIS® technique in Australia after visiting French orthopaedic surgeon Dr Frederick Laude in Paris in 2007.

The published data in the orthopaedic literature and the Australian National Joint Replacement Registry clearly shows that more experienced surgeons have better patient outcomes. This is particularly relevant for the AMIS® method which is regarded as a technically more demanding procedure compared to other approaches to the hip.

Total hip replacement is a safe and reliable procedure that is used to treat painful and debilitating arthritic and post traumatic conditions of the hip joint. The operation relieves the pain and restricted movement, thereby allowing the patient to return to the activities of daily living pain free. Total hip replacement is indicated for patients that have failed non-operative treatment options.

The prosthetic implant consists of the acetabular component, the femoral component and the bearing or articular interface (ball and socket).

The acetabular component is placed into the pelvis after the hip socket has had any residual cartilage removed and the bone prepared using an instrument called a reamer.

Dr Glase rarely cements the acetabular component preferring to use uncemented (bone ingrowth) components. These are usually made from titanium. The femoral component fits into the femur (thigh bone) after the femoral head has been removed and the femur prepared with instruments called broaches. Dr Glase usually prefers cementless fixation with titanium implants. He will sometimes use cement depending on the bone quality.

There are four different bearing surfaces

  • metal ball on polyethylene acetabular liner
  • ceramic ball on polyethylene liner
  • ceramic ball on ceramic liner
  • metal ball on metal liner

Preferences

Dr Glase does not recommend metal on metal. Recent studies have shown significant failure rates with metal on metal bearings. Dr Glase has been a long standing advocate of ceramic on ceramic or ceramic on polyethylene. The type of prosthesis and bearing interface will be discussed in detail at the time of consultation.

The direct anterior approach was first described by German surgeon Dr Karl Hueter in 1881. The Judet Operating table was designed by French Surgeon Henri Judet in 1943. French surgeon, Dr Robert Judet performed the first hip replacement via the direct anterior approach in 1947 using the Judet table.

15 years ago, French orthopaedic surgeon Dr Frederick Laude developed specific instruments and a leg holder based on the principals of the Judet operating table to make a technically demanding procedure easier and truly minimally invasive (AMIS®). Dr Glase visited Dr Laude in July 2007 and pioneered this technique in Australia.

The approach is between two muscles at the front of the hip; tensor fascia lata and rectus femoris. There is no damage to the gluteal muscles which are the main providers of power and stability to the hip. There is no damage to the short external rotator muscles at the back of the hip which are very important for hip stability. The nerve supply to the muscles is undamaged and so muscle function is minimally affected.

Advantages of the anterior approach

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Reduced postoperative pain

3,4,7,11,12,13

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Rapid rehabilitation times

4,5,6,7,14,15,16,17,18

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Better functional results

7,8,9,14,16,17

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Reduced dislocation Rates

10,19,20,21,22

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Better prosthesis positioning

14,19

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Reduced blood loss

2,4,7

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Reduced hospital stay

1,2,3,4,5

1. Rachbauer F et al. The History of the Anterior Approach to the Hip. Orthop Clin North Am. 2009 Jul; 40(3): p311-20 | 2. Kreuzer S et al. Single incision anterior approach for total hip arthroplasty: Smith-Peterson approach. Limited Incisions for Total Hip Arthroplasty. AAOS Rosemont. P 1-14. 2007. | 3. Pfirrmann C et al. Abductor tendons and muscles assessed at MR Imaging after total hip arthroplasty in asymptomatic and symptomatic patients. Radiology. 2005 Jun; 235(3): p969-76 | 4. Bremmer AK et al. Soft tissue changes in hip abductor muscles and tendons after total hip replacement: Comparison between the direct anterior approach and the transgluteal approaches. JBJS Br. 2011 Jul; 93(7): P886-9 | 5. Dora C et al. MR Imaging of the abductor tendons and muscles after total hip replacement in asymptomatic and symptomatic patients. EFFORT 2007, Florence, Italy. May 11-15. | 6. Muller DA et al. Anterior minimally invasive approach for total hip replacement: Five year survivorship and learning curve. Hip Int. 2014 | 7. Dora C. Der anteriore Zugang fur die minimal invasive HTPE. Leading Opinions, Orthopadie 1. 2006 | 8. Dora C Minimalinvasive Zugangean an der Hufte ( Minimally invasive approaches in hip surgery ). Orthopaedie Mitteilungen 6/07: p574-6 | 9. Dora C et al. Muscular damage after total hip arthroplasty : conventional versus minimally invasive anterior approach. Podium presentation at the 68th Annual Scientific Meeting of the AOA, Australia, October 12-16,2008 | 10. Siguier T et al. Mini incision anterior approach does not increase dislocation rate: a study of 1037 consecutive total hip replacements. CORR. 2004 Sept; (426): p164-73 | 11. Goebel S et al. Reduced postoperative pain in total hip arthroplasty after minimally invasive anterior approach. Int Orthop. May 2011 | 12. Alecci V et al. Comparison of primary total hip replacements performed with a direct anterior approach versus the standard lateral approach: perioperative findings. J Orthop Traumatol. 2011 Sept 12(3): p123-9 | 13. Rachbauer F. Minimally invasive total hip arthroplasty: anterior approach. Orthopaede. 2006 Jul 35(7): p723-4, 726-9 | 14. Nakata et al. J Arthroplasty. 2008 | 15. Meneghini R et al. Muscle damage during MIS total hip arthroplasty : Smith- Peterson versus posterior approach. CORR. 2006 Dec 453: p293-8 | 16. Field R. Gait analysis study. Br Hip Society, Manchester 2012 | 17. Giannine et al. SICOT 2007 | 18. Matta J et al. Orthop Clin N Am.2009(40): p351-6 | 19. Matta J et al. CORR. 2005(441): p115-24 | 20. Keggi et al. JBJS Am. 2003 | 21. Sariali et al. J Arthroplasty. 2008 23(2); p266-72 | 22. Anterior Total Hip Arthroplasty Collaborative Orth Clin N Am 2009

Who is suitable for AMIS®

A frequently asked question is “are all hip replacements suitable for the AMIS® method?” Since 2007 Dr Glase has performed over 2500 primary total hip replacements via the AMIS® technique and only two by other approaches that were considered unsuitable for AMIS®.

In the hands of a competent surgeon experienced in the AMIS® method, the majority of primary hip replacements can be performed safely via the direct anterior approach. This includes those with abnormal anatomy including hip dysplasia, Perthes disease and previous trauma.
The very obese patient and the heavily muscled younger male patient can both safely undergo hip replacement surgery via the AMIS® method.

Typical operating time is between 40 and 60 minutes. Typical hospital stay is 3 days. The key however to a successful hip replacement is to choose an experienced and skilled hip surgeon. This is especially true if considering the direct anterior approach which is recognised as being a more technically demanding procedure.

Other surgical approaches

There are several other approaches used to perform total hip replacement surgery. These include the posterior, lateral and anterolateral approaches.

The posterior, lateral and anterolateral approaches to the hip all cut, split, divide or detach muscle from bone and potentially damage the nerve supply to the muscles. The posterior approach is not Dr Glase’s preferred method. This technique involves splitting the gluteus maximus and tensor fascia lata muscles and entering the hip joint from the back.

This involves further muscle damage to the gluteus minimus and a very important group of muscles called the short external rotators. These muscles play a very important role in hip stability. Dislocation rates following a posterior approach vary between 3 and 4 % according to the published literature.

The anterolateral approach involves splitting the gluteus maximus and tensor fascia lata muscles and detaching gluteus minimus and part of the gluteus medius off the femur. The nerve supply of these muscles is at risk. A permanent limp and joint stiffness is not uncommon.

Potential Complications

The vast majority of patients who undergo total hip replacement recover without any complications and obtain a pain free hip with a full functional range of movement and return to a full and active lifestyle. Complications following surgery are rare, but include:

Infection.
Deep infection involving the prosthesis is uncommon with rates reported in the literature of around 1%. Infection can rarely spread from other parts of the body to the prosthesis. It is advisable that any necessary dental procedures be undertaken prior to surgery. Acute infection can be treated by surgical washout. Rarely revision of the prosthesis is necessary.

Loosening.
This is where the bond between the bone and the prosthesis fails. This is rare but can be corrected with further surgery.

Deep Vein Thrombosis (DVT).
Despite all steps to prevent DVT, including early postoperative mobilisation, thromboembolic compression stockings and blood thinning medication following surgery, some patients will still develop a DVT. Pulmonary embolism is where a blood clot travels to the lung. This is a very uncommon complication and requires longer treatment with blood thinning medication.

Dislocation.
This is where the ball comes out of the socket. This can occur especially in the first six weeks after surgery, usually when the hip is placed in an extreme position. Dr Glase and the physiotherapists at the hospital will advise you on a few simple precautions in the first six weeks to avoid this. Dislocation rates with the anterior approach in most reported series are less than 1%. This is significantly lower than the 3 to 4% reported dislocation rates for the posterior approach. Dr Glase is aware of two dislocations in his series of over 2500 anterior cases.

Fracture.
Periprosthetic fracture is uncommon and usually follows a fall in the early postoperative period. Those most at risk are the very elderly and those with significant osteoporosis. Treatment may involve further surgery.

Nerve injury.
Areas of numbness on the skin around the surgical wound occur occasionally. This usually resolves over time. Injury to the Sciatic, Femoral or Obturator Nerve causing a loss of motor function is a very rare complication.

Systemic medical complications
Such as stroke, heart attack or allergic reaction to medication are uncommon.

Leg length inequality.
The cause for leg length discrepancy is often related to concerns regarding dislocation. This is particularly relevant with the posterior approach where the external rotator muscles are detached and stability is thus compromised. The operated leg is often lengthened to compensate for this loss of dynamic hip stability. With the direct anterior approach these muscles are not compromised. Combined with the more predictable acetabular cup placement with the anterior approach, the concerns regarding dislocation are not so great and so leg length inequality is less of a problem.

Dr Glase will discuss the potential risks and complications in detail at the time of consultation.

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