Introduction
Orthopedic conditions of the pelvic limb are some of the most frequently diagnosed causes of lameness in the dog. As our understanding of rehabilitation therapy and sports medicine grows, “new” conditions are being identified, and new means of treatment are being used. This chapter offers a brief overview of the more common pelvic limb conditions. Knowledge of pertinent anatomy, physical examination findings, and appropriate diagnostic tools allows for an accurate diagnosis and proposal of treatment options. Insight with respect to prognosis and expected recovery is discussed for individual procedures. More in-depth discussion of these conditions is readily available elsewhere.
Iliopsoas Strain
Anatomy
The iliopsoas muscle represents the fusion of the psoas major and iliacus muscles (Figure 14.1). The psoas major arises from the transverse processes of L2 and L3 and the bodies of L4–7. The iliacus arises from the ventral surface of the ilium. The two muscles combine and have a common insertion on the lesser trochanter of the femur. The action of this muscle is hip flexion with external femoral rotation and lumber flexion (Evans, 1993a).
Figure 14.1 Iliopsoas muscle anatomy. The iliopsoas muscle represents the fusion of the psoas major and iliacus muscles.
(Illustration by Faith Lotsikas.)
Pathophysiology
Iliopsoas muscle strains are believed to occur during eccentric contraction, when the muscle is contracting while lengthening (Breur & Blevins, 1997; Nielsen & Pluhar, 2005). The weakest area and therefore where strains most often occur is the muscle–tendon junction near the insertion on the lesser trochanter of the femur. The strain may be a primary injury or secondary to an underlying orthopedic or neurological condition. Slipping into abduction, jumping out of a vehicle, aggressive training, and roughhousing with other dogs may be precipitating events.
Diagnosis
Lameness ranges from subtle intermittent offloading to continuous significant lameness and is exacerbated by activity. Performance-related issues such as knocking bars, taking wide sweeping turns, or slowing in the weave poles during agility competition are common complaints from clients.
Tightness, discomfort, and spasm may be noted on direct palpation of the myotendinous unit (Figure 14.2), or when stretching the muscle by placing the hip in extension with abduction and internal rotation of the limb (Figure 14.3).
Figure 14.2 Tightness, discomfort, and spasm may be noted on direct palpation of the myotendinous unit of the iliopsoas.
Figure 14.3 Tightness, discomfort, and spasm may be noted when stretching the muscle by placing the hip in extension with abduction and internal rotation of the limb.
Pelvic radiographs are generally unremarkable. Avulsion of the lesser trochanter may be noted with acute traumatic events, and mineralization within the tendon or at the tendinous insertion may be seen with chronic cases. Advanced diagnostics may be used to confirm the diagnosis. Ultrasonography is an excellent modality to diagnose strains and allows for monitoring the response to treatment.
Treatment
Conservative medical management and rehabilitation therapy are recommended for acute iliopsoas strains. Medical management includes nonsteroidal anti-inflammatory drugs (NSAIDs), muscle relaxants, cryotherapy, and restricted activity. Surgical treatment by tenotomy may be warranted when there are irreversible changes to the myotendinous unit that are nonresponsive to medical management and rehabilitation therapy.
Gracilis and Semitendinosus/Semimembranosus Myopathy
Introduction
Myopathy of the gracilis, semitendinosus, or semimembranosus may occur individually or concurrently. There is usually no definitive episode reported by the owner/handler. There does appear to be some breed and age predilection, with highly active German Shepherd Dogs and related breeds between the ages of 3 and 7 years overrepresented (Vaughan, 1979; Lewis et al., 1997; Steiss, 2002).
Anatomy
The gracilis, semitendinosus, and semimembranosus muscles form an extensive broad muscular sheet that is found superficially in the caudal portion of the inner thigh (Figure 14.4). The gracilis arises from the pelvic symphysis and inserts on the proximal medial tibia. An aponeurosis extends to the crural fascia and from its caudal border sends a well-developed reinforcing band to the calcanean tendon, which attaches to the tuber calcaneus. This muscle is responsible for thigh adduction, hip extension, stifle flexion, and tarsal extension (Evans, 1993b).
Figure 14.4 The gracilis, semitendinosus, and semimembranosus muscles form an extensive broad muscular sheet that is found superficially in the caudal portion of the inner thigh.
(Illustration by Marcia Schlehr.)
Pathophysiology
In most cases, the etiology of gracilis/semitendinosus/semimembranosus myopathy is unknown. Numerous theories exist, including acute trauma, chronic repetitive trauma, autoimmune disease, drug reaction, infection, neurogenic disorders, and vascular abnormalities (Taylor & Tangner, 2007). Ischemia secondary to indirect trauma may also lead to fibrosis and contracture (Taylor & Tangner, 2007). Histologically, the affected muscle is replaced by dense, collagenous connective tissue (Taylor & Tangner, 2007).
A 2002 study involving canine athletes suggests that excessive activity can lead to muscle strains resulting in inflammation, edema, localized hemorrhage, and eventually, fibrosis (Steiss, 2002). German Shepherd Dogs may be at greater risk of muscle strain during physical activity due to the increased angulation (flexion) at the stifle (Steiss, 2002).
Diagnosis
Presentation of gracilis, semitendinosus, or semimembranosus contracture is very unique and consistent in appearance. The diagnosis can be made with a thorough history, observation of gait, and physical examination (Figure 14.5). Affected dogs have a pelvic limb gait abnormality characterized by a shortened stride with a rapid, elastic medial rotation of the paw, internal rotation of the tarsus with external rotation of the calcaneus, and internal rotation of the stifle during the mid-to-late swing phase of protraction.
Figure 14.5 Dogs with gracilis myopathy have a pelvic limb gait abnormality characterized by a shortened stride with a rapid, elastic medial rotation of the paw, internal rotation of the tarsus with external rotation of the calcaneus, and internal rotation of the stifle during the mid-to-late swing phase of protraction. A. Elastic medial rotation of the left pelvic limb paw and external rotation of calcaneus. B. 0.5 seconds later, the paw has rotated laterally and the calcaneus medially.
(Images derived from video.)
A taut, firm band is palpable in the caudomedial aspect of the thigh. Pain and spasm may be noted when performing a stretch of the gracilis–semitendinosus muscle complex (hip flexion, stifle extension, and limb abduction; Figure 14.6). In severe cases, the stifle cannot be fully extended (Figure 14.7).
Figure 14.6 In dogs with gracilis myopathy, pain and spasm may be noted when performing a stretch of the gracilis–semitendinosus muscle complex (hip flexion, stifle extension, and limb abduction).
Treatment
For acute cases, conservative management and rehabilitation therapy consisting of NSAIDs, restricted controlled activity, cryotherapy, manual therapy, and modalities is recommended.
Treatment options are limited for chronic cases. Eighteen dogs with gracilis or semitendinosus myopathy were treated with various methods (Lewis et al., 1997). Eight received medical management alone or prior to surgery. There was no apparent response. Fifteen dogs were treated with one or more surgical procedures. Lameness resolved following transection, partial excision or complete resection of the affected muscle. However, lameness recurred 6 weeks to 5 months following surgery. Adjunctive medical treatment did not change the outcome. Myectomy of the entire gracilis muscle is no more successful as the gait abnormality may return within three to 5 months due to semitendinosus involvement (Lewis et al., 1997).
At present, long-term rehabilitation therapy is the treatment of choice. Therapy may include chronic treatment with continuous ultrasound therapy, manual therapy, and a home therapeutic exercise program. Unfortunately, it is rare for rehabilitation therapy to completely resolve the clinical signs. With continued rehabilitation therapy and dedication to the home maintenance program, working dogs with this condition can remain active.
Hip Dysplasia (HD)
Pathophysiology
Hip dysplasia (HD) can be defined as abnormal development of the hip joint, resulting in coxofemoral laxity due to decreased coverage of the femoral head by the acetabulum and ineffective soft tissue stabilization of the joint (Demko & McLaughlin, 2005; Lopez, 2012). Abnormal kinematics result in joint capsule stretching, cartilage erosion, subchondral bone fracture, periarticular fibrosis, and new bone formation (Dassler, 2003). Disease progression results in degenerative and inflammatory changes characteristic of osteoarthritis (OA) (Dassler, 2003).
Hip dysplasia is the most common developmental orthopedic condition in dogs and is highly breed dependent (Witsberger et al., 2008; Smith et al., 2012). Despite attempts at eradication of the condition through selective breeding programs, the prevalence of HD remains very high within certain breeds (Coopman et al., 2008; Witsberger et al., 2008; Smith et al., 2012). A review of over 1.2 million dogs between 1964 and 2003 reported the prevalence and risk factors for HD in over 50 breeds (Witsberger et al., 2008). Newfoundlands, Rottweilers, German Shepherd Dogs, and retrievers are among the most commonly affected breeds with prevalence up to 17% (Witsberger et al., 2008). Smith et al. followed a colony of Labrador Retrievers over their life span and found that despite breeding for an expected HD incidence between 26% and 51%, in fact, 98% of the dogs had evidence of HD at the time of death (Smith et al., 2012). These studies highlight the fact that HD is a complex condition with many factors involved in the development, progression, and recognition of the disease.
Hip dysplasia is a polygenic, heritable condition, in which the phenotypic expression can be influenced by reproductive status, age, body condition and conformation, diet and other environmental factors (Spain et al., 2004; Demko & McLaughlin, 2005; Witsberger et al., 2008; Smith et al., 2012). Castrated male dogs are significantly more likely to be effected by HD, and an association has been shown between gonadectomy at <5 months of age and the development of HD in both males and females (Spain et al., 2004; Witsberger et al., 2008).
Kealy and Smith et al. found that the development and progression of HD was significantly delayed or decreased in dogs maintained at a lean body condition through caloric restriction compared to litter-matched pairs of a higher body condition score (Kealy et al., 2002; Smith et al., 2012). When all dogs in this study were pooled, a linear relationship was seen between age and prevalence of HD. A conclusion of this study was that selecting breeding dogs based on phenotype (young age, lean body condition) does not ensure elimination of the HD genotype (Smith et al., 2012).
Diagnosis
Dogs with HD often show clinical signs following a bimodal curve: 4 months to 3–4 years, and >7 years of age (Witsberger et al., 2008; Smith et al., 2012). Puppies and young dogs with HD present with a history of decreased activity or reluctance to jump or climb stairs, bunny-hopping gait, underdeveloped pelvic limbs with a narrow stance, and pain or vocalization with manipulation (Dassler, 2003; Demko & McLaughlin, 2005). Mature dogs with symptoms related to OA of the hips show varying degrees of lameness that are worse after rest and heavy exercise. They also are reluctant to jump, and have pelvic limb atrophy and behavioral changes associated with pain (Demko & McLaughlin, 2005).
The diagnosis of HD is based on physical examination and radiographic findings (Demko & McLaughlin, 2005). Passive hip laxity can be palpated in young dogs using the Ortolani maneuver (Demko & McLaughlin, 2005; Gatineau et al., 2012) (Figure 14.8). This test may be inaccurate in dogs younger than 4 months, as maximal laxity is present between the ages of 2–6 months (Smith et al., 1998; Gatineau et al., 2012).
Figure 14.8 Passive hip laxity can be palpated in young dogs using the Ortolani maneuver.
Illustration by Marcia Schlehr.
The sensitivity and specificity of a positive Ortolani sign detected at 6 months for development of hip OA at 2 years have been shown to be 100% and 50%, respectively (Gatineau et al., 2012). In other words, all dogs with hip OA at 2 years had a positive Ortolani at 6 months, and half of the dogs with a positive Ortolani showed radiographic signs of OA at 2 years. Furthermore, a negative Ortolani sign at 6 months is significantly predictive of lack of OA at 2 years (Gatineau et al., 2012).
In mature dogs with HD, physical exam findings typically include uni- or bilateral weight-bearing pelvic limb lameness, pelvic limb muscle atrophy and gluteal weakness, prominence of the greater trochanter consistent with femoral head subluxation, decreased passive and active extension of hip, and core muscle weakness (Demko & McLaughlin, 2005; Bockstahler et al., 2012).
There are several radiographic views used to assess hip conformation and secondary OA (Powers et al., 2010; Gatineau et al., 2012; Verhoeven et al., 2012). The standard ventrodorsal (VD) extended limb view is widely used, and is the view required by the Orthopedic Foundation for Animals (OFA) for screening (Figure 14.9).
Figure 14.9 For radiographic diagnosis of hip dysplasia, the standard ventrodorsal (VD) extended limb view is widely used, and is the view required by the Orthopedic Foundation for Animals (OFA) for breed screening.
There are several limitations to the VD view and the OFA screening methodology. Positioning for this view underestimates the degree of joint laxity. Additionally, radiographs are given a subjective rating based on assessment of joint conformation, laxity, and degenerative changes in dogs at least 2 years of age. Lastly, submission of radiographs to OFA by breeders and veterinarians is optional; consequently, underestimation of the prevalence of HD is likely (Powers et al., 2010; Gatineau et al., 2012; Verhoeven et al., 2012).
Other radiographic views have been developed to objectively diagnose HD earlier in the disease process (Powers et al., 2010; Gatineau et al., 2012; Verhoeven et al., 2012). PennHIP® (PennHIP, Philadelphia, PA) measures joint congruity by calculating the relative displacement of the femoral head from the acetabulum during coxofemoral distraction, thus accounting for passive joint laxity (Powers et al., 2010). The calculated distraction index (DI) predicts the likelihood of the dog developing OA compared to other dogs of the same breed (Runge et al., 2010). PennHIP has been validated as a reliable screening tool in dogs as young as 6 months (Powers et al., 2010). When compared directly, OFA underestimates the susceptibility to OA compared to PennHIP (Powers et al., 2010). The Norberg angle, dorsal acetabular slope (DAS), and dorsolateral subluxation view (DLS) are other objective methods of evaluating HD (Gatineau et al., 2012; Verhoeven et al., 2012).
Nonsurgical Management
Nonsurgical management involves a multimodal approach including activity modification, pain management, maintenance of a lean body condition, pharmacologic modulation of joint disease, therapeutic modalities, physical rehabilitation, and regenerative and complementary medicine.
A systematic review of the veterinary literature regarding nonsurgical management of HD found high levels of evidence in support of weight management through dietary restriction, parenteral administration of polysulfated glycosaminoglycans (PSGAGs), and adipose-derived stem cell therapy (Kirkby & Lewis, 2012). Additional techniques that have been shown to be effective include acupuncture, extracorporeal shock wave therapy (ESWT), and omega 3 fatty acid supplementation (Roush et al., 2010).
At the time of this publication, scientific evaluation of the efficacy of physical rehabilitation, including therapeutic exercise and hydrotherapy, in the management of HD and OA in dogs has not been investigated. However, considering the role of passive joint laxity in the pathogenesis of HD, it is logical to assume that strengthening of the soft tissue support structures of the hip would be beneficial. In fact, German Shepherd Dogs are more likely to develop hip OA at a lower DI (less passive laxity) than more well-muscled breeds such as Rottweilers (Gatineau et al., 2012). Initiation of a comprehensive rehabilitation program for a dog with HD will likely prove successful either alone or complementary to surgical intervention.
Surgical Management
Joint Preservation Procedures
Greater degrees of hip laxity correlate with an increased likelihood of secondary OA but not necessarily clinical disability. There are two surgical procedures that aim to improve the clinical signs associated with coxofemoral laxity in skeletally immature dogs.
Juvenile Pubic Symphysiodesis (JPS)
Juvenile pubic symphysiodesis (JPS) causes premature closure of the pubic symphysis. This procedure results in ventral rotation of the dorsal acetabular rim as the remaining growth plates continue to grow. This technique will reduce the risk of progression of HD in cases of mild to moderate hip laxity but is significantly less effective in addressing more severe laxity. In puppies with more severe laxity, the progressive correction of acetabular orientation would fail to capture the femoral head. JPS should be performed before 16 weeks of age to improve hip stability (Patricelli et al., 2002; Bernarde, 2010). Consequently, JPS is recommended in dogs that are unlikely to have any contemporary disability from HD. Dynamic imaging of the hips to demonstrate laxity (e.g., hip distraction with PennHip) should guide selection or exclusion of the individual dog as a candidate for JPS.
Triple Pelvic Osteotomy (TPO) and Double Pelvic Osteotomy (DPO)
Triple pelvic osteotomy (TPO) and double pelvic osteotomy (DPO) aim to increase dorsal acetabular rim coverage of the femoral head. This is achieved by making two or three osteotomies around the acetabulum, manually rotating the acetabulum over the femoral head, and stabilizing it with a plate and screws (Figure 14.10). It is ideally performed in dogs less than 5–8 months of age with an angle of relocation < 25–30° and a quality of Ortolani sign that suggests no erosion of the dorsal acetabular rim. Dogs with clinical lameness are less likely to be optimal candidates for TPO/DPO, but there is understandable reluctance to perform corrective osteotomy on dogs with hip laxity that is an incidental finding on physical examination.
Figure 14.10 Triple pelvic osteotomy (TPO) aims to increase dorsal acetabular rim coverage of the femoral head. This is achieved by making two or three osteotomies around the acetabulum, manually rotating the acetabulum over the femoral head, and stabilizing it with a plate and screws. Pre-operative (A) and post-operative (B) radiographs.
Patients typically bear weight on the surgical leg immediately following surgery. The most common complication with this procedure is implant loosening and pelvic canal narrowing (Whelan et al., 2004; Doornink et al., 2006). The recent use of locking implants has decreased the complication rate with this procedure (Rose et al., 2012). Postoperative exercise restriction is imperative until radiographic evidence of bony union is present, at which time therapy aimed at building muscle mass can be initiated. Range of motion is typically preserved with this procedure, though gait kinematics reveals a base narrow stance that is usually permanent.
The progression of OA remains possible with both the JPS and TPO procedures, particularly in patients that already have damage to the round ligament or cartilage (Holsworth et al., 2005; Manley et al., 2007) (Figure 14.11).
Figure 14.11 The progression of OA remains possible with both the JPS and TPO procedures, particularly in patients that already have damage to the round ligament or cartilage.
Salvage Procedures
Total Hip Replacement (THR)
Total hip replacement (THR) is routinely used to target lameness caused by HD/OA that is refractory to medical management. THR involves surgical removal of the patient’s acetabulum and femoral head and replacement with a polyethylene cup and metallic stem and head. The expected outcome is restoration of normal hip function, range of motion, and pelvic and crural muscle bulk. It is unusual that osteoarthritic degeneration will preclude THR. However, there is an increased complication rate and degree of difficulty associated with THR performed in patients with chronic dorsal luxation secondary to HD. In such cases, the window of opportunity for routine THR may be short.
Selection criteria for THR are stringent, and common contraindications to THR include obesity, bacterial pyoderma, other clinically significant orthopedic disease, neurological impairment, infective arthritis, immunosuppression, and polyarthropathy. Resolution of some of these conditions is practical and may allow THR at a later date if necessary.
There are currently two categories of hip replacement. One involves the use of bone cement, which binds the implant to the bone. The other is a cementless system that requires bone integration or growth into the implant (Figure 14.12). Patients may also benefit from a hybrid hip, which is a combination of a cementless acetabular cup with a cemented stem (Figure 14.13).
Figure 14.13 Hip replacement using a hybrid hip, which is a combination of a cementless acetabular cup with a cemented stem.
The primary advantage of the cemented system is that it offers maximum strength shortly after implantation. It is ideal for patients with more brittle bone or straight shaft femurs, as seen typically in the older shepherd breeds. It can also be used successfully in small dogs and cats (Liska, 2010). With time, the cement mantle can separate from the bone (aseptic loosening), which can be caused by inflammation at the bone–cement interface, or less commonly, at the cement–implant interface (Finkelstein et al., 1991; Edwards et al., 1997). The risk of infection is higher, as bacteria can sequester in the cement.
Cementless hip systems rely on bone ingrowth or ongrowth of the implants for long-term stability. Cementless systems theoretically offer a long-term advantage of decreased aseptic loosening and carry a smaller risk of infection. However, perioperative complications are reported to be higher than with a cemented hip, and long-term data are currently not available to document the true life span of these implants (Guerrero & Montavon, 2009; Lascelles et al., 2010).
Postoperative Management.
Most patients will bear weight on the operated limb within 24 hours of surgery. The first 4–6 weeks postsurgery are the most critical. During this time, the joint capsule is healing, and in a cementless hip, osteointegration is taking place. Patients are prone to coxofemoral luxation and subsidence during this time. Rehabilitation therapy is not recommended until radiographs demonstrate stable implants 1 month following surgery. Off-leash activity is not recommended until 12 weeks following surgery.
FHO
Femoral head and neck ostectomy (FHO) is a salvage procedure in which the head and neck of the femur are removed, eliminating the bone-on-bone contact of the femoral head and acetabulum (Figure 14.14). This procedure relies on periarticular fibrosis and muscle to support the body weight of the patient. There are few perioperative complications, as no implants are present (Dueland et al., 1977). Patients may have a residual gait abnormality, but are usually perceived as pain free by their owners, and can maintain an acceptable level of activity (Off & Matis, 2010).
Figure 14.14 Femoral head and neck ostectomy (FHO) is a salvage procedure in which the head and neck of the femur are removed, eliminating the bone on bone contact of the femoral head and acetabulum.
Postoperative Management.
Functional shortening of the limb associated with dorsal displacement of the femur, failure to recover normal muscle mass and decreased range of hip motion are likely causes of poor outcome with the FHO. Most patients will not bear weight on the limb for 3–5 days following surgery. Rehabilitation therapy is imperative for a functional outcome. Long-term administration of analgesic medication and early therapy (5–14 days following surgery) aim to improve comfort and preserve range of motion of the hip (Grisneaux et al., 2003). Once the patient is adequately bearing weight, strength training is initiated. Underwater treadmill therapy can be extremely beneficial and is recommended starting 2–3 weeks following surgery. Swimming tends to be less beneficial in these cases, as patients are often hesitant to fully engage the surgical limb. Recovery is usually longer than that experienced with a THR, typically 16–20 weeks until optimal function is achieved. The most predictable outcome with this procedure occurs with a thin, well-conditioned patient.
Coxofemoral Luxation
Anatomy
The coxofemoral joint derives most of its stability from the round ligament of the femoral head, the joint capsule, and the dorsal acetabular rim. The joint also receives ancillary stabilization from the ventral labrum, surrounding musculature and the adhesion–cohesion relationship of the joint surfaces and synovial fluid. Disruption of two or more primary stabilizers results in luxation of the hip (Holsworth & DeCamp, 2003).
Pathophysiology
Hip luxation is most often due to a traumatic event, such as vehicular trauma (Bone et al., 1984; Basher et al., 1986; Demko et al., 2006). This results in disruption of the round ligament of the femoral head and joint capsule, with ensuing luxation of the hip. The gluteal and iliopsoas muscle groups act upon the greater and lesser trochanters, causing the femoral head to move in a craniodorsal direction (Basher et al., 1986). Ventral luxation is less common, and is usually a result of a slip or fall causing the stifle to be abruptly abducted. Underlying HD is a predisposing factor for both types of luxation (Herron, 1979).
Diagnosis
The affected patient is often nonweight bearing, with external rotation of the stifle and adduction of the lower limb. The affected limb appears shorter, with a prominent hard swelling (the greater trochanter) palpable above the coxofemoral joint. Diagnosis is made upon examination and palpation, and is confirmed with radiographs (Figure 14.15). The patient is thoroughly evaluated for concurrent injuries commonly seen with traumatic events.
Figure 14.15 Radiograph showing typical appearance of coxofemoral luxation.
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