Minimally Invasive Two-incision Total Hip Replacement

December 20, 2010 | Emerging Technology Reports

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Proprietary names: MIS 2-Incision Generic procedure names: minimally invasive total hip arthroplasty (THA); small-incision THA; two-incision THA

Minimally invasive two-incision (MIS-2) total hip replacement (THR) involves supplanting a damaged hip socket (acetabulum) and top of the thigh bone (femoral head and neck) with a prosthesis.1-3 MIS-2 THR involves making one 3.8 to 8.0 cm incision for acetabular preparation and a second 1.5 to 6.0 cm incision to implant the femoral prosthesis.4,5 During this procedure, the surgeon does not dissect muscles but separates them along their natural intervals using finger tips and retractors.4,5 This muscle sparing aspect is the procedure's key distinguishing feature.6,7 MIS-2 THR is an alternative to conventional THR and minimally invasive one-incision (MIS-1) THR. Conventional THR involves a 15 to 25 cm incision and results in extensive soft-tissue damage and muscle dissection.2,8 Although the incision provides a wide view of the surgical field and facilitates prosthesis implantation, it results in significant postprocedure pain, a lengthy hospital stay, and reduced function for the patient.9 MIS-1 THR requires one 6 to 10 cm incision that dissects muscle and tendons.6,7,10,11 Purported advantages of MIS-2 or MIS-1 THR over conventional THR include the following:12-14

Purported advantages of MIS-2 THR over MIS-1 THR include the following:15

A potential disadvantage of these minimally invasive approaches compared to conventional THR is the restricted view of the surgical area, which makes the procedure more difficult for surgeons and increases the likelihood of femoral fractures.2,14 Specialized, smaller instrumentation is available for minimally invasive THR, including the following:

Some surgeons assert that these instruments decrease complications and minimize soft-tissue damage.14 Others perform minimally invasive hip replacement using conventional instruments.9,16

For MIS-2 THR, anesthesiologists place patients under general or spinal anesthesia.7,8,17 The patient lies in the supine position, and the surgeon uses fluoroscopy to locate the femoral neck.5,17-19 The surgeon makes the anterior incision directly over the femoral neck.5,18-21 Next, the surgeon removes the damaged femoral head to access the acetabulum, places lit retractors around the acetabulum, and uses low-profile reamers to hollow out the acetabulum.5 Fluoroscopy is used to confirm that the acetabulum has been reamed to the appropriate degree.5 Using an acetabular cup impactor, the surgeon tests cups of various sizes before selecting the final cup and the appropriate liner.22 The surgeon secures the polyethylene liner to the cup and may use screws to strengthen the fixation of the acetabular components.5,23-25

Next, the surgeon prepares to place the femoral component by making the second incision posterior to the femoral canal.5,18-21 The surgeon retracts the muscle and exposes the femoral cavity using fluoroscopy to visualize the proximal femur.18 The surgeon gradually enlarges the femoral cavity so that the implant can be securely seated.22 Trial neck and head sizes are tested, and once the final size is determined, the surgeon uses a broach handle to enlarge the femoral canal and allow for implant insertion. Surgeons secure femoral components with or without cement. For cementless applications, the surgeon uses components that are treated with materials, such as hydroxyapatite, to encourage bony ingrowth.22 Lastly, the surgeon attaches the femoral head to the implant, places the head into the acetabular liner, and rotates the hip to check mobilization and positioning.17,26 Operative times for MIS-2 THR vary but can last up to four hours.26

Because MIS-2 THR provides only a limited view of the surgical area, some surgeons use computer-assisted navigation software for accurate component positioning. These systems allow surgeons to visualize obscured anatomy, calculate the optimal implant placement, and measure leg lengths.27

Recovery and rehabilitation practices vary; some physicians allow their patients to walk on the day of the procedure, while others do not permit ambulation until the next day.17,19,28,29 Clinicians assess patients several hours after surgery to establish an exercise and gait training regimen. Full weight bearing on the operative leg is encouraged.17 To be discharged, patients must be able to walk with assistive aids and navigate stairs.17,29 Upon discharge, clinicians administer heparin or aspirin and fit patients with compression stockings to prevent deep vein thrombosis.17,19,23,30,31

Inpatient

Patients require THR because their hip has been damaged by osteoarthritis, osteonecrosis, rheumatoid arthritis, or post-traumatic arthritis.1,10,32 In the...

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