Patient Education and Consent
It is imperative to ensure appropriate patient education before either conventional total hip arthroplasty (THA) or minimally invasive THA (MIS-THA). Such education should address the patient’s postoperative expectations, as well as inform the patient regarding the administration of anticoagulation. Preoperative counseling with respect to the patient’s postoperative activity level is left to the discretion of the surgeon.
Preprocedural Planning
Provided that the disadvantages caused by limited visualization during MIS-THA can be overcome, there is no logical reason to use a longer incision and create more surgical trauma if a shorter incision with less trauma would achieve the same end result. The skin incision can limit component insertion. A 10-cm (4-in.) incision is appropriate for inserting a 56-mm acetabular component while avoiding contact between the component and the skin or subcutaneous tissues. [9]
The most important factors allowing early discharge appear to be related to patient selection, patient motivation, anesthesia, acute pain-management techniques, and the postoperative protocol. The specific operative approach used does not appear to be an independent factor in early discharge. There are no data to indicate how the surgical approach interacts with the other variables in affecting discharge.
Factors such as family education, patient preconditioning, preemptive analgesia, and accelerated preoperative rehabilitation—rather than the surgical technique per se—may play a major role in fostering better outcomes after MIS-THA. Careful scientific study and evaluation are warranted before MIS techniques are widely accepted.
Preprocedural evaluation
No special workup is indicated for MIS-THA patients as compared with conventional THA patients. If the diagnosis of hip disease is in doubt, magnetic resonance imaging (MRI) or a diagnostic injection into the hip joint may be useful. If a fluoroscopically guided hip-joint injection relieves pain, the pathology is probably localized to the intra-articular joint. Careful examination and selected diagnostic modalities may be needed to rule out spinal stenosis, herniated lumbar disk, vascular claudication, incarcerated hernia, meralgia paresthetica, psoas impingement, hip bursitis, transient osteoporosis, malignancy, stress fracture, and other diseases that can mimic the symptoms of hip degeneration.
A routine preoperative workup is necessary, including the following:
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Complete medical workup
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Radiography (eg, affected extremity and chest radiographs)
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Basic laboratory evaluation (eg, type and screen, complete blood count, basic metabolic panel, and urine analysis)
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Electrocardiography (ECG) for patients older than 50 years
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Additional studies, as warranted by any comorbid conditions that may be present
Dental evaluation and treatment for dental diseases should be done before THA is performed. Routine cleaning of the teeth should be delayed for several weeks after surgery. In older patients with prostate problems or urinary retention issues, urinalysis should be done and cultures obtained to check for urinary infections; any infections diagnosed should be treated before THA.
Because of the limited surgical exposure afforded by MIS-THA, preoperative templating is critical. Templating may be used to guide determination of the following:
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Implant size
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Leg length restoration
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Femoral stem offset
If there is uncertainty about leg lengths, computed tomography (CT) can provide definitive evaluation. The opposite hip joint should be evaluated on the anteroposterior radiograph for comparison of leg lengths and assessment of existing offset relations. In selected patients, other studies (eg, vascular indices, spinal radiographs, MRI of the hip or spine, and evaluation of the ipsilateral knee joint) may be required.
Intraoperative radiographic imaging may or may not be necessary, depending on surgeon experience. Intraoperative radiography may prolong operating time and complicate the procedure, but it may reduce the risk of component malpositioning and facilitate the estimation of leg length.
Equipment
Specialized surgical instrumentation and implants are commonly required for MIS-THA. Because exposure may be limited, MIS-THA may necessitate modification of conventional instrumentation and possibly the use of additional equipment (eg, fiberoptic light cables, cutaway reamers, angled reamers and broach handles, Hohmann retractors with light sources, or flexible acetabular reamers). [71, 72, 73]
Particular operating room tables make certain MIS-THA approaches more accessible and may be required to provide the requisite traction and permit rotation of the lower extremity. For example, a Judet Orthopaedic Table (Tasserit, Sens, France) or a PROfx Fracture Table (OSI, Union City, CA) can facilitate an anterior approach, and a Jupiter Table (Trumpf, Charleston, SC) may be especially suitable for an anterolateral approach. [24, 72, 74]
Monitoring & Follow-up
After an MIS-THA procedure, the patient should be followed at the same time intervals that would be appropriate for a conventional THA. Periodic clinical and radiographic examinations are indicated to monitor for aseptic loosening, wear, and late infection.
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Minimally invasive total hip arthroplasty. Shown are skin incisions for direct anterior (black), miniposterior/lateral/anterolateral (dark blue), conventional posterior (dark blue plus red extensions), direct superior (green), and SuperPATH (purple) approaches to hip. Conventional posterior incision is usually 10-25 cm long. Single incisions for minimally invasive approaches are usually less than 10 cm long. In two-incision approach, both incisions are usually less than 5 cm long.
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Minimally invasive total hip arthroplasty: two-incision approach. Photograph of right hip in supine position showing outlines of anterior superior iliac spine and greater trochanter. Dotted line marks anterior incision.
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Minimally invasive total hip arthroplasty: direct anterior approach. Insertion of acetabular component after acetabular component reaming in supine position.
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Minimally invasive total hip arthroplasty: direct anterior approach. Circumferential view of acetabular component is shown with visual confirmation of orientation. Insertion guides and radiographs also may be used to assess positioning.
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Minimally invasive total hip arthroplasty: direct anterior approach. View of proximal femur and right hip in supine position, showing lesser trochanter femoral neck resection marked with pen.
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Minimally invasive total hip arthroplasty: direct anterior approach. Photograph of right anterior thigh after draping on fracture table. Note metal spar with square holes; this device attaches to fracture table and allows elevation of femur during femoral preparation.
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Minimally invasive total hip arthroplasty: direct anterior approach. Left femoral head is dislocated anteriorly before osteotomy of femoral neck.
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Minimally invasive total hip arthroplasty: direct anterior approach. Proximal femoral exposure and rasp is introduced into femoral canal facilitated by fracture table via metal spar elevating femur anteriorly.
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Minimally invasive total hip arthroplasty: two-incision approach. Surgeon can guide femoral broaches through small posterior incision while palpating through anterior incision.
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Minimally invasive total hip arthroplasty: two-incision approach. After wound closure, length of anterior incision is approximately 7.5 cm (3 in.).
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Minimally invasive total hip arthroplasty: direct superior approach. Gluteus maximus fascia is incised sharply to expose gluteus maximus muscle.
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Minimally invasive total hip arthroplasty: direct superior approach. Gluteus maximus muscle fibers are divided longitudinally, and deep gluteus maximus fascia is divided to expose pericapsular fat; prirformis tendon is detached close to its insertion.
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Minimally invasive total hip arthroplasty: direct superior approach. Capsule is incised in inferior aspect of wound; capsulotomy is extended posterior and superior to superior acetabulum.
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Minimally invasive total hip arthroplasty: direct superior approach. Hip is dislocated, femoral neck osteotomized, and femoral head removed.
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Minimally invasive total hip arthroplasty: direct superior approach. Sharp curved Hohmann retractor is placed over anterior acetabular rim; second bent 90-degree Hohman at inferior margin; 90-degree handheld retractor in superior aspect of wound; and 90-degree sharp Hohmann deep to superior capsule. Optional retractor may be placed on posterior aspect of acetabulum.
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Minimally invasive total hip arthroplasty: direct superior approach. Acetabular labrum is excised; acetabulum is reamed. Retractor is placed in inferior aspect of wound to retract quadratus femoris away from proximal femur.
