• DVT: <1 per cent
• Infection: <1 per cent
• Femoral neck fracture: incidence related to amount of femoral ‘bump’ removed
• Avascular necrosis of the femoral head: unknown incidence (many studies of open surgery show 0 per cent)
• Heterotopic ossification: 3 per cent
• Progression to frank osteoarthritis: up to 100 per cent
lateral with the leg in maximal internal rotation best demonstrate the anatomy. Magnetic resonance imaging (MRI), MR arthrography or arthroscopy are often used to examine for labral pathology. Conventional arthrography and local anaesthetic injection are frequently used to provide evidence that the pain is originating in the hip.
The surgeon must decide the approach to be taken. There are three common options:
• The arthroscopic approach (see ‘Hip
arthroscopy’, next section).
• The lateral open approach, using a trochanteric flip osteotomy, as popularized by Ganz. The hip is then dislocated to reveal the impingement.
• A more recent approach has been a ‘mini-open’ modified Smith–Peterson approach. This has the advantage of visualization without dislocation of the hip. This approach is described below, as an example.
Normal
Pincer
CAM
Mixed
Anaesthesia and positioning
Anaesthesia is general with supine positioning. The use of an intraoperative image intensifier is optional.
SURGICAL TECHNIQUE
Landmarks
The anterior superior iliac spine is palpated. Slight external rotation of the hip aids location of the interval between the tensor fascia lata and sartorius.
Incision
A 7–10 cm incision is created, running from just below the anterior superior iliac spine, running in the border between the tensor fascia lata and sartorius. This should not stray medially into the area overlying sartorius and it is preferable to create the incision a few millimetres lateral to the border of sartorius to ensure that this does not occur. The direction of incision is towards the lateral border of the patella.
Superficial dissection
Dissection is continued through fat and superficial fascia. The lateral femoral cutaneous nerve is identified, running over the fascia between the tensor fascia lata and sartorius. The nerve is retracted medially and the fascia incised between the two muscle bellies. This provides an interval with the muscle belly of the tensor fascia lata laterally and that of the sartorius medially.
The dissection is continued down between the tensor fascia lata and sartorius, until the direct and reflected heads of the rectus femoris are identified.
Structure at risk
• Lateral femoral cutaneous nerve
Deep dissection
The reflected head of the rectus femoris is identified and dissected off its origin on the superior acetabular margin. Its fibres also blend with the anterior hip capsule and these fibres are dissected free from the capsule. The direct head is retracted medially to reveal the iliopsoas tendon. This also requires dissection free from the capsule as it is attached by the iliocapsularis tendon. Subsequently, this too can be retracted medially.
The underlying capsule is exposed and can be incised in line with the femoral head–neck junction. This is most easily identified at the anteromedial portion of the femoral head as the impingement bump in a cam-impinging hip will prevent palpation of the head–neck junction laterally. Thus, it is advisable to begin the incision medially and proceed laterally.
PROCEDURE
The osteoplasty of the head–neck junction is carried out with a small (10–15 mm) osteotome. An assistant internally and externally rotates the hip to allow complete excision of the bump. The resection is directed distally to produce a bevelled resection, restoring the offset between the femoral head and neck. This creates a ‘V’- shaped valley over the anterior head–neck junction. The depth of the valley can be assessed by bringing the hip back into the position of the impingement test. The aim is a gain in both internal rotation and flexion of the hip by over 10°. If the valley is not deep enough, it can be further deepened in a similar manner. The aim is complete excision of the protuberant bump, until the remaining femoral head is spherical and no
Structures at risk
• Femoral nerve and artery – these lie medial to the sartorius, anterior to the pectineus muscle. They will not be damaged if dissection is lateral and deep to the sartorius
• Medial femoral circumflex artery – 1 cm proximal to the lesser trochanter, underlying the iliopsoas tendon. If not identified and accidentally damaged, profuse bleeding can be expected
longer impinging on the anterior acetabular rim. Similarly, if there is evidence of pincer impingement, the acetabular osteophytes or calcified labral tissue can be removed with an osteotome and excised.
Bleeding from exposed bone can be reduced by application of bone wax. The wound is thoroughly irrigated and any loose bone and cartilage carefully removed.
Closure
• The capsulotomy is closed with absorbable suture.
• The reflected head of rectus femoris is reapproximated with absorbable suture.
• The tensor fascia lata–sartorius interval is closed with absorbable suture.
• Skin closure.
POSTOPERATIVE CARE AND
INSTRUCTIONS
The patient may begin mobilization as soon as comfortable – this should be touch- weightbearing, with crutches, for 6 weeks. Active flexion is avoided for 6 weeks to allow healing of the reflected head of rectus femoris. Active abduction is begun straight away. Mobilization without crutches is slowly begun after 6 weeks. High-impact sports, including running, are not permitted for 6 months.