The most common indication for arthroscopy of the hip joint is young dogs with hip dysplasia to assess articular cartilage condition prior to performing corrective pelvic osteotomy surgery (Holsworth et al. 2005), either triple pelvic osteotomy (TPO) or double pelvic osteotomy (DPO). Arthroscopy provides more information for case selection and for improving results with TPO/DPO surgery than can be obtained with other less invasive techniques. The patient is prepared for the TPO/DPO surgery, and arthroscopy is performed as the first step of the procedure. If the patient is found to be a good candidate for TPO/DPO with arthroscopy, the surgery is performed. If the patient is not a good candidate for TPO/DPO based on the arthroscopic findings, the procedure is terminated and the patient is recovered. Other indications for hip joint arthroscopy are hip joint pain or crepitus not associated with hip dysplasia, radiographic evidence of intra‐articular fractures, degenerative changes not typical of hip dysplasia (Luther et al. 2005), hip luxation (Segal et al. 2018), or periarticular lytic lesions. Since the most common indication for hip joint arthroscopy is in dysplastic dogs immediately prior to TPO/DPO surgery, the patient is clipped, positioned on the table with the leg suspended, prepared, and draped for the TPO/DPO surgery. The monitor is placed cranial to the patient, and the surgeon stands dorsal to or at the caudal end of the table with the assistant on the ventral side of the patient (Figure 2.8). Alternatives are to place the monitor dorsal to the patient far enough cranially to be out of the way of the sterile field for surgery and for the surgeon to stand at the caudal end of the patient with the assistant ventral to the patient. Positioning is the same for other indications unless a planned operative procedure dictates otherwise. All portals for the hip joint are on the dorsal aspect of the joint (Figure 6.1). The telescope portal is placed directly dorsal to the greater trochanter, and an egress needle or portal is placed either cranial or caudal to the telescope portal. Access to the hip joint is very easy in young dysplastic dogs because of the hip laxity. To establish the telescope portal, ventral traction is applied to the limb and the proximal femur is pushed down or medially. A 2″ to 3″ 20‐gauge spinal needle is inserted into the joint in a medial direction immediately dorsal to the greater trochanter, joint fluid is aspirated, and the joint is distended with saline. A stab incision is made in the skin, fascia, and muscle at the portal site with a no. 11 scalpel blade, the portal tract is deepened with blunt dissection using a curved mosquito hemostat, and the telescope cannula is placed into the joint using the blunt obturator (Figure 6.2). With the joint positioned as described, there is adequate space for positioning the telescope (Figure 6.3). For joint exploration prior to TPO/DPO surgery, egress through the initial arthrocentesis needle or a second needle is adequate and establishing an egress portal is not required. Operative procedures are not commonly performed in the hip joint, and an operative portal is not typically placed but if needed can be placed either cranial or caudal to the telescope portal. A hip distraction device was evaluated for use when adequate distraction is not possible (Devesa et al. 2014). Figure 6.1 Portal sites on the dorsal aspect of the hip joint. The three portal sites shown are the dorsal telescope portal (asterisk) with craniodorsal and caudodorsal operative or egress portal sites (Triangles). Source: Modified from Freeman (1999) Modified Drawing. © John Wiley & Sons. Figure 6.2 Positioning of the telescope vertically into the joint space for examination of the joint. Source: Modified from Freeman (1999) Modified Drawing. © John Wiley & Sons. The sciatic nerve courses across the dorsolateral aspect of the pelvis medial and dorsal to the hip joint and then continues caudally to bend around the caudal aspect of the joint. The sciatic nerve lies a sufficient distance from the hip joint so there is little risk of damage during placement of the dorsal telescope portal (Figure 6.1). The caudal operative or egress portal is closer to the nerve placing it at risk but with the portal location technique using a needle observed with the telescope risk is minimal. Figure 6.3 An anterior–posterior drawing of the hip joint demonstrating positioning of the telescope. Source: Modified from Freeman (1999) Modified Drawing. © John Wiley & Sons. Figure 6.4 The medial aspect of the femoral head articular surface seen to the lower left, the medial concave portion of the dorsal aspect of the central or dorsal acetabular articular surface seen to the upper right, and the round ligament seen in the center background are used for orientation in the joint. The telescope is looking medially from a lateral portal with dorsal to the upper right and cranial to the upper left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 6.5 The cranial aspect of the acetabular articular surface is filling the top of the image and the cranial aspect of the femoral head articular surface is seen to the lower left. The cartilage surfaces are normal. There is very mild disruption of the labrum of the acetabulum in the upper right aspect of the image. The telescope is looking craniomedially from a lateral portal with dorsal up on the image and cranial is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 6.6 The central or dorsal portion of the acetabular articular surface is seen in the background with the dorsal aspect of the femoral head articular surface filling the bottom of the image. A small portion of the lateral acetabular rim is seen out of focus in the upper right. The telescope is looking craniomedially from the lateral portal with dorsal up and medial to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 6.7 The cranial tip of the acetabular articular surface is seen in the lower left of the image, a small portion of the cranial aspect of the femoral head articular surface is in the upper left and the cranial end of the ventral acetabular ligament is running horizontally across the center of the picture. A small portion of fat in the acetabular fossa is visible in the lower left. The telescope is looking medially from a lateral telescope portal with lateral up on the image and cranial is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 6.8 The caudal tip of the acetabulum in the center background seen articulating with the caudal aspect of the femoral head to the lower left and showing attachment of the dorsal joint capsule in the upper right of the picture. The telescope is looking caudally from a lateral portal with dorsal up on the image and lateral to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 6.9 The dorsal rim of the acetabular articular surface seen with the dorsal acetabular articular surface in the lower left, the dorsal acetabular rim curving across the center of the image, the dorsal cartilaginous labrum seen as a band of rounded tissue slightly darker than the acetabular cartilage, and dorsal joint capsule on the right. The telescope is looking cranially from a lateral telescope portal with dorsal to the upper right and lateral to the upper left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 6.10 The dorsal aspect of the femoral head is filling the lower left half of the image with the acetabular articular surface in the upper right. This area of the femoral head is the area of most importance in assessing acceptance for pelvic osteotomy surgery because this will be the new weight bearing surface after surgery. The telescope is looking cranially from a lateral portal with lateral to the upper left and dorsal to the upper right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 6.11 The dorsal margin of the femoral head articular cartilage seen as a white band running at an angle across the upper center of the image, the dorsal aspect of the intra‐articular femoral neck is visible as slightly pink tissue with small blood vessels filling the lower left of the picture, and dorsal joint capsule is in the background on the upper right. The telescope is looking cranially from a lateral telescope portal with dorsal up and lateral to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 6.12 The round ligament is running vertically across the center of the image, originating in the acetabular fossa at the top, and inserting on the fovea capitis of the femoral head at the bottom. The telescope is looking medially from a lateral telescope portal with dorsal up and cranial to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 6.13 The cranial joint space in a dog with the cranial aspect of the femoral head seen on the far left, the acetabular articular surface in the lower right, and the joint capsule with slightly increased blood supply filling the upper center of the image. Minor degenerative changes are seen in this picture as a slight roughening of the margin of the articular cartilage in the right center of the image. This change is secondary to an old untreated fracture but the lameness in this dog was due to a partially ruptured cranial cruciate ligament. The telescope is looking craniomedially from a lateral telescope portal with lateral up and cranial to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 6.14 The ventral joint space of the hip is seen in the background beyond the femoral head at the top of the picture, the caudal acetabular cartilage is in the lower left, the transverse acetabular ligament is seen indistinctly as a white band running to the right from the tip of the acetabular cartilage, and acetabular fossa fat is seen to the right between the acetabular cartilage and the transverse acetabular ligament. The telescope is looking medially from a lateral telescope portal with lateral up on the image and cranial to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 6.15 The dorsal femoral neck is seen filling the bottom left of the image with attachment of the dorsal joint capsule curving away from the bone at the far left and extending across the top of the image. The cranial joint capsule is visible in the background. A small portion of femoral head cartilage curves down in the lower right of the picture. The telescope is looking cranially from a lateral portal with dorsal up on the image and medial to the right. There is a small amount of reaction in the joint capsule on the femoral neck secondary to hip dysplasia. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Areas of primary interest with arthroscopy of the hip in young dysplastic dogs prior to performing pelvic osteotomy surgery are the joint surfaces that will come into use with repositioning of the acetabular cup. These areas include the dorsal surface of the femoral head, the dorsal margin of the femoral articular surface with the femoral neck, and the central portion of the acetabular articular surface. The cartilage wear pattern on the femoral head from subluxation is evaluated for extent, severity, and position. The typical wear pattern is on the medial aspect of the femoral head immediately dorsal to the fovea capitis and can appear as fine (Figure 6.16) or coarse fibrillation (Figure 6.17), partial‐thickness cartilage erosions (Figures 6.18 and 6.19), variable sized full‐thickness cartilage loss (Figure 6.20), and lesions with eburnation of exposed bone that can be either circular (Figure 6.21) or linear (Figure 6.22). Small lesions in this area, on the medial aspect of the femoral head (Figures 6.16–6.20), do not interfere with joint function following acetabular repositioning, but large lesions in this area (Figure 6.21) and any lesions on the dorsal or dorsomedial area of the femoral head (Figure 6.23) decrease the prognosis for good function following surgery. Significant osteophytes on the dorsal rim of the femoral head and femoral neck (Figure 6.24) can interfere with a range of joint abduction following acetabular repositioning. Acetabular osteophytes form primarily in the acetabular fossa as either flat bone filling the fossa (Figure 6.25) or as raised more typical osteophytes on the ventral margin of the fossa (Figure 6.26). Changes in the acetabular articular surface secondary to hip subluxation are seen as a roughened cartilage surface (Figure 6.23), loss of dorsal acetabular rim cartilage, and bone secondary to wear from subluxation of the femoral head (Figure 6.27
6
Hip Joint
6.1 Patient Preparation, Positioning, and Operating Room Setup
6.2 Portal Sites and Portal Placement
6.3 Nerves of Concern with Hip Joint Arthroscopy
6.4 Examination Protocol and Normal Arthroscopic Anatomy
Orientation in the hip joint utilizes the round ligament, the concave articular surface of the acetabulum, and the convex articular surface of the femoral head (Figure 6.4). A common tendency is to insert the arthroscope too deeply so that the tip is in the tissues of the acetabular fossa obscuring identification of structures needed for orientation. Retraction of the telescope will bring the anatomy into view. The joint is examined in a systematic manner (Video 6.1) to assess the entire articular surface of the acetabulum including the cranial extent (Figure 6.5), central portion (Figure 6.6), caudal end of the transverse acetabular ligament (Figure 6.7), caudal tip of the acetabulum (Figure 6.8), and dorsal acetabular rim with the labrum and attached joint capsule (Figure 6.9). The articular surface of the femoral head is examined with particular attention given to the dorsal surface (Figures 6.6, and 6.10), medial surface immediately dorsal to the fovea capitis (Figure 6.4), and the dorsal margin of the articular surface on the femoral neck (Figure 6.11). Soft tissue structures that are evaluated include the dorsal labrum of the acetabulum and dorsal joint capsule (Figure 6.9), round ligament (Figure 6.12), ventral acetabular ligament (Figure 6.7); the cranial (Figure 6.13), caudal (Figure 6.8), and ventral (Figure 6.14) joint compartments; and the dorsal femoral head and neck (Figure 6.15).
6.5 Diseases of the Hip Diagnosed and Managed with Arthroscopy
6.5.1 Hip Dysplasia
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