MODIFICATION TO WATSON-JONES ANTERO-LATERAL MINI-INCISION

Abstract

The purpose of mini-invasive hip arthroplasty is least damage to skin and muscles. Unlike Roettinger modification to Watson-Jones, our approach requires no special table or instruments. Besides, direction of skin incision is perpendicular to interval between glutei and tensor muscles, thus called a Crisscross Approach. Potentially, a cross shape exposure allows a larger view and therefore a lesser damage to skin and muscles during retraction. Skin incision, being in line with the femur (almost parallel), allows expansion of incision proximally and distally. No tendon or muscles are severed achieving a true inter-muscular minimally invasive approach.

After working with 3 cadavers to perfect the technique and with investigation and research board (IRB) approved consent, 40 prospective patients underwent mini-invasive crisscross technique from December 06–June 07 with 6 months follow up. A standard non-cemented hip was implanted. Previously disrupted hip muscles patients were excluded. Patients were positioned in a lateral decubitus with pelvis secured and flexed 20°–30°. Incision started 2 inches inferior and posterior to ipsilateral anterior superior iliac spine (ASIS) extending distally for 3 inches or more for obese or muscular patients. Acetabulum is exposed using curved Hohmann retractors one above and one below femoral neck after excising most of the anterior capsule with releasing the superior and inferior capsule. The femoral neck is osteotomised as routine extracting the femoral head. Then the same curved retractors are placed behind anterior and posterior rim of acetabulum with an optional third curved retractor may be placed at the inferior rim. The acetabulum is reamed with the usual straight reamers and the cup is then implanted as routine. Angled reamers are not necessary as our skin incision is in line with the reamer direction. Femoral neck exposure starts with the surgeon positioned anterior to pelvis. Paralysis of the muscles is confirmed with anesthesiologist and table is tilted 20°–30° posteriorly. Hip is then extended 20°–30°, externally rotated to 80°–90° and adducted with a retractor underneath femoral neck. Another curved retractor is placed gently on greater trochanter to protect glutei. Leg is allowed to drop in a bag. Canal finder and use of box osteotome is helpful to avoid breaching the femoral cortex or varus positioning of the stem. Broaching or reaming and final implant insertion is done as routine. Hip reduction is achieved as routine by reversing the table tilt and bringing the leg forward with traction and internal rotation.

36 out of 38 eligible patients were sent home after their rehab goals were met in 4 therapy sessions (2–3days). Full weight bearing was allowed in 4 weeks. One stem was undersized, two were in slight varus, and total blood loss was less than 5 gm/dl of Haemoglobin at post op day three. No dislocation or complications related to exposure. No neurovascular injury and no re-operation. Surgery time averaged 20 minutes longer mainly at femoral exposure. As experience is gained the time is lessened. Post-operative intravenous morphine pump administration was stopped in 24 hours in 82% of patients after surgery instead of the 48 hour routine.

Crisscross approach differs by transecting no tendon or muscles, requiring no special table or instruments with incision that gives more exposure, allows expansion and reduces skin damage resulting in true non-invasive approach. Exposure of the femur was difficult in the first few cases. Tilting the operating table posteriorly, releasing superior and inferior capsule as has been recommended by previous authors helped femoral exposure. Recovery from surgery in terms of rehab sessions and postoperative pain control were improved compared to our previous standard of care. Long term follow up is under current research investigation.