The incidence of nerve injuries varies greatly according to the studies. It can reach up to 20 %, when authors consider temporary neuropraxia, with pudendal nerve palsy being the most frequent [2].

Pudendal neuropraxia is secondary to the nerve compression between the perineal support and the pubic ramus. It appears prematurely after arthroscopy, often by perineal hypoesthesia or dysesthesia [37].

Sciatic and peroneal nerve injuries remain unusual. They are secondary to stretching forces on the nerves, during the traction. Telleria [38] has monitored the sciatic nerve during hip arthroscopy and found sciatic nerve dysfunctions increasing after 32 min of traction, with traction force superior to 22.7 kg. The patient complains of dysesthesia on the lateral aspect of the leg and dorsum of the foot, with weakness of ankle dorsiflexion.

These injuries generally solve spontaneously in few days to 6 months. Long-term sequelae are exceptional.

The overall rate of perineal skin damage is approximately 2/1000 [2]. It is secondary to a prolonged and important compression of the skin between the pubis ramus and the perineal support.

The injuries can be ranging from edema or hematoma to skin necrosis and pressure sore (Fig. 17.3). It can affect the perineum (scrotum and labia), the skin of the groin, and the inner part of the thigh.

It is the same process as for the formation of bedsores, in accelerated procedures. This complication delays the hip rehabilitation, but again the long-term sequelae remain very rare.

To limit complications secondary to traction, two points are essential:

To overcome the traction-related complications, Sadri has described satisfying results with a hip distractor, an equivalent of external fixator, fixed on the acetabulum and femoral diaphysis [44]. Nevertheless, other specific complications to this technique are described.

Direct trauma of neurovascular structures can occur during portal placement, since every entry point is near neurovascular structures, in particular when the leg is under traction. The anterior portal is close to the lateral femoral cutaneous nerve (average distance, 5 mm), to the femoral nerve (average distance, 24 mm), and to the femoral artery (average distance, 39 mm) [45, 46]. The posterolateral portal is near the sciatic nerve at the level of capsule (average distance, 29 mm); and the anterolateral portal can come close to the superior gluteal nerve.

The lateral femoral cutaneous nerve, the nearest structure to the anterior portal, is at greatest risk of injury. Its incidence can reach 1 %, according to studies [45, 47]. It manifests by a numbness sensation in the anterolateral part of the thigh.

Knowledge of the anatomy around the hip joint is the best preventive measure of these complications. Neutral positioning of the leg is important during portal placement to ensure that the anatomy is not distorted.

Iatrogenic labral or chondral injuries are the most common complication of hip arthroscopy. The rate of this complication is very approximate and probably underreported by surgeons [2, 48, 49], varying from 0.67 to 20 % for labral injuries and from 0.3 to 39 % for chondral injuries, according to published studies.

The labral penetration is generally realized during establishment of the initial anterolateral portal, when performing central compartment first approach. It is localized in the superior or anterosuperior part of the labrum. The spinal needle can go through the labrum when it is placed too close to the acetabulum. The guidewire, and then the cannula, will follow the same track. The tear of the labrum will then have the same size as the diameter of the cannula (Fig. 17.4). On the other hand, positioning the needle too close to the femoral head can lead to direct chondral damage by the needle or the cannula. The second portal is typically safe since the needle penetrates in the joint under direct visualization by arthroscope.

Some indications of hip arthroscopy are more at risk to cause chondrolabral injuries, such as labral detachment, where the labrum occupies a large part of the joint space, or stiff hips, when sufficient distraction of 10 mm is not possible.

Once the surgeon has penetrated into the joint, there is less danger of labral damage, but chondral lesions can still occur. The repetitive exchange of instruments, in particular without the use of a cannula, and bad portal placement are risk factors of femoral head cartilage injuries. Acetabular cartilage injuries can also occur by intra-articular penetration of anchors, during labral repair.

These damages are immediately visualized during the arthroscopy. Badylak and Keene have shown that iatrogenic labral punctures do not affect the clinical results at short term, with a follow-up of 2 years or more [48]. However, their long-term consequences on the cartilage wear patterns have not been studied.

Peripheral compartment first approach allows reducing the risk of chondrolabral lesions, comparing to central compartment first approach [42]. Indeed, during peripheral approach, the instrumentation is introduced along the anterior femoral neck, at a safe distance to the labrum and cartilage. The capsulotomy is performed safely until the capsulolabral junction, which is easily visualized. Then, central compartment access can be performed under direct vision.

To diminish risk of chondrolabral lesions when performing central compartment first approach, the needle and cannula should be inserted into the joint under fluoroscopic guidance, in order to obtain the best position level to penetrate the hip. Byrd has described a fluoroscopic sign to control if the needle has punctured the labrum during the portal placement [50]. After the needle has penetrated into the joint, a saline solution is injected. The needle should move distally with the femoral head, checked under fluoroscopy. If the needle stays proximal, a labral perforation is probable. The position of the needle should then be changed.

In order not to force the passage inside the hip with the hazard to create iatrogenic chondral lesions, instrument exchange should always be performed with a cannula. Also, to avoid intra-articular penetration of anchors, the position and direction of the drill should be carefully controlled before drilling. Hernandez [51] and then Lertwanich [52] have described the safe position for suture anchor insertion. The ideal starting point for anchor insertion is located on the capsular side of labral insertion, which is between 2.3 and 2.6 mm from the edge of the acetabular rim. The angle formed by the long axis of the drill and a perpendicular to the acetabular face is considered safe when it is between −7.2° and 20.4°, according to acetabular rim location and anchor size less than 3 mm. Nevertheless, drilling should always be supervised under arthroscopic vision of the acetabular articular surface

A survey of the MAHORN group has identified 40 cases of intra-abdominal fluid extravasation on 25,648 hip arthroscopies, with an incidence of 0.16 % [53]. According to other studies, the rate of this complication can reach 3/1000 [2]. This complication is probably due to the irrigation fluid diffusion along the iliopsoas sheath. The extravasation is generally retroperitoneal, sometimes intraperitoneal.

Possible risk factors can be a prolonged operative time (2 h or more), a high pressure of the irrigation fluid, an iliopsoas tenotomy at the beginning of the procedure, an extended capsulotomy, and the presence of an acetabular fracture [53].

Symptoms vary depending on the amount of extravasation volume. Verma et al. described five warning signs that must alert the surgeon and anesthetist during the surgery: inability to distend the joint, increased fluid requirement to maintain distension, frequent cutoff of pump irrigation systems, abdominal and thigh distension, and acute hypothermia [54]. In the recovery room, the patient can present with abdominal pain and distension, dyspnea, hypothermia, hemodynamic instability, and/or decreased venous return circulation from the lower extremities. Ultrasound or CT scan can confirm the diagnosis.

The preventive measures are to reduce the operative time, to limit the capsulotomy, to delay iliopsoas tenotomy to the end of surgery, to limit pump pressure 40–50 mmHg, to be cautious during hip arthroscopy for acute acetabular fractures, and to evaluate frequently the abdomen and the patient’s hemodynamic status.

The risk of mechanical failure is high, compared to other joints, with an incidence varying between 0.2 and 3.5 % according to the studies [2, 33, 34].

The most frequent is instrument breakage (Fig. 17.5) due to the need to use long instruments, often fragile, subjected to high stresses in this deep joint. Suture anchor failure is also described, due to the narrowness of the anterior acetabular rim [51].

To limit the risk, the needle, the Nitinol guidewire, the shaver, and the burr are usually disposable. Also, a sufficient capsulotomy increases instruments mobility, reducing stresses on the devices. Anchor placement should be controlled and resistance to manual traction should be tested before suture deployment.

In case of instrument breakage or anchor failure, the latter need to be removed, sometimes by arthrotomy, since they can cause serious chondral injuries.