**4. Acetabular and femoral abnormalities**

Biomechanical abnormalities at the acetabulum and femur are a key factor to consider in borderline cases between hip preservation surgery or THA. Some biomechanical abnormalities contra-indicate or increase the risk of complications for hip arthroscopy and would be better addressed through osteotomy surgeries. However, an osteotomy surgery may not be a good option for a patient when considering the chondral damage, patient age and presence of low back pain. In addition, some patients will not be willing to undergo an osteotomy when considering the surgery magnitude and recovery. Therefore, acetabular and femoral biomechanical abnormalities will influence the decision on conservative management, hip arthroscopy, hip osteotomy or THA. These treatment option should be considered as a continuum of treatment for many patients, as more invasive procedures are recommended when less invasive interventions fail.

#### **4.1 Acetabular dysplasia**

The presence of acetabular dysplasia and its severity is to be considered before recommending a hip arthroscopy procedure versus other treatment options. Hip arthroscopy as isolated treatment for moderate to severe acetabular dysplasia has been associated with poor outcomes [14, 15]. However, hip arthroscopy with capsule repair has demonstrated good outcomes for patients with borderline hip dysplasia, traditionally described as lateral center-edge angle between 20° and 25° [16, 17]. Domb et al. reported the results of hip arthroscopy in 22 patients with lateral centeredge angle between 18° and 25°, and no or mild osteoarthritis (Tönnis grade 0 or 1) [16]. The authors utilized a combined imbrication and inferior capsular shift of the iliofemoral ligament to close the hip capsule arthroscopically. Good to excellent results were reported in 77% of the patients at a mean follow-up of 28 months, with 2 patients (9%) requiring revision surgery due to repeat sports injury or trauma [16]. The mean Tönnis angle of 5.8°, within normal limits, and the absence of significant osteoarthritis are important to consider on the results reported by Domb et al. [16]. Fukui et al. described the results of hip arthroscopy in 28 patients with lateral centeredge angle between 15° and 19°, at a mean follow-up of 42 months [17]. Five patients (18%) with a mean joint space <2 mm before hip arthroscopy underwent THA at a mean follow-up of 24 months after the hip arthroscopy [17]. Two patients (7%) required a periacetabular osteotomy to treat dysplasia after failure to improve following hip arthroscopy, while other two patients required a revision hip arthroscopy [17]. The mean Tönnis angle in patients who required periacetabular osteotomy after hip arthroscopy was 21°, while those not requiring PAO had a mean Tönnis angle of 15°. Fukuda et al. concluded that major surgery following hip arthroscopy is more likely for older patients, male, with more severe dysplasia, and with a larger alpha angle and

decreased joint space [17]. Uchida et al. studied 28 patients with acetabular dysplasia who underwent hip arthroscopy [18]. The authors reported that patients with a broken Shenton line, femoral neck-shaft angle >140°, lateral center-edge angle <19°, or BMI >23 kg/m2 at the time of surgery are not good candidates for the arthroscopic management of acetabular dysplasia [18]. A major limitation of the studies by Domb, Fukui and Uchida et al. is the lack of consideration for the femoral torsion [16, 17]. Larson et al. reported inferior results of hip arthroscopy in 88 dysplastic hips when compared to non-dysplastic hips treated for femoroacetabular impingement [19]. The authors defined failure as a modified Harris Hip Score (mHHS) ≤70 or eventual pelvic/femoral osteotomy or total hip arthroplasty. At the time of final follow-up, the dysplastic cohort demonstrated a mean mHHS of 81.3 with a mean 15.6-point improvement in mHHS, compared with 88.4 and 24.4 points, respectively, in the femoroacetabular impingement cohort [19]. Larson et al. also reported that increased femoral torsion and psoas tenotomies did not influence the outcomes in hips with acetabular dysplasia [19].

Periacetabular osteotomy (PAO) is another option for patients with acetabular dysplasia that should be considered for some patients to preserve the hip joint, prolong the native hip life, or as a bridge to a THA. Studies on long term results have provided insight on when is too late for a PAO. Matheney et al. reported the outcomes of PAO in 135 hips at an average follow-up of 9 years [20]. Two independent predictors of failure (defined as arthroplasty or a high pain score) were identified: (1) an age of more than thirty-five years and (2) poor or fair preoperative joint congruency [20]. The probability of failure requiring arthroplasty was 14% for hips with no predictors of failure, 36% for those with one predictor (either an age of more than thirty-five years or poor or fair joint congruency), and 95% for those with both predictors [20]. Wells et al. reported the outcomes of PAO in 154 hips at an average of 10.3 years post-operatively [21]. One hundred and twenty-two hips (79%) did not undergo THA and did not have significant hip symptoms at the final follow-up [21]. A higher risk of failure was associated with fair or poor preoperative joint congruency and with overcorrection (a postoperative lateral center-edge angle of >38°) [21].

Association of hip arthroscopy and periacetabular osteotomy is another option of treatment for patients with acetabular dysplasia. Hip arthroscopy after a PAO surgery is required in 3.1–27% according to different authors [22, 23]. In patients with hip dysplasia who fail hip arthroscopy, PAO has been shown to be successful and results did not differ from patients who undergo PAO as index procedure [24].

A frequent question from patients is if undergoing a PAO or hip arthroscopy would decrease the chances of success for a THA procedure in the future. Considering THA after a PAO, the medical literature is controversial. Amanatullah et al. reported no difference in complication, revision rates or clinical results for THA in dysplastic patients with or without prior PAO [25]. Osawa et al. reported poorer clinical outcomes of THA in patients with prior PAO compared to dysplastic patients without PAO, although there was no difference in revision or complication between the groups [26]. Both studies observed increased rates of acetabular component malposition in hips with prior PAO [25, 26]. In regards to results of THA following hip arthroscopy, Lemme et al. reported that patients who underwent THA more than 1 year after hip arthroscopy were at no increased risk for surgical or medical complications [27]. However, increased risk of dislocation (OR 1.75; CI 1.05–2.87; P = .03) and aseptic loosening (OR 2.18; CI 1.06–4.49; P = .03) was observed if the THA was performed <1 year after the hip arthroscopy [27]. THA <1 year after hip arthroscopy was also

*Decision Making in Borderline Cases between Hip Preservation and Reconstruction Surgery DOI: http://dx.doi.org/10.5772/intechopen.104765*

associated with increased risk for needing revision THA at 2 years (OR 1.92; CI 1.07–3.36; P = .02) and 4 years (OR 2.05; CI 1.17–3.53; P = .01) after THA.

The severity of hip dysplasia is usually defined by the morphologic features of the acetabular roof. However, abnormalities of the acetabular horns and sagittal orientation of the acetabulum are also frequent and have not been studied regarding the results of hip preservation surgery. Further studies are necessary to define if hips with antero-inferior or posteroinferior acetabular undercoverage have inferior results with hip arthroscopic procedures (**Figure 3**). Abnormal acetabular slope (sagittal orientation of the acetabulum) is another factor that requires further investigation when recommending a preservation or reconstruction procedure (**Figure 4**).

#### **4.2 Femoral torsion and acetabular version abnormalities**

Assessment in three planes is a basic requirement for any project in engineering. The hip joint is a complex biomechanical construct, and evaluation in three anatomical planes should be completed before any surgical recommendation. The imaging assessment of the hip joint has historically neglected the axial plane due to the inherent limitations of radiographs. Currently, the broad availability of MRI and CT to orthopedic surgeons makes it difficult to justify the lack of imaging assessment in three anatomical planes (axial, coronal and sagittal). The femoral torsion is one of the hip parameters assessed in the axial plane and has not received the necessary attention by clinicians and researchers in the orthopedic field. Increased femoral torsion is associated with decreased extension and external rotation, and increased internal rotation of the hip [30–35]. Decreased femoral torsion is associated with increased external rotation and decreased internal rotation of the hip [30–33]. Effects of abnormal femoral torsion on the lumbopelvic biomechanics have also been reported, and can be estimated by the hip-spine extension and flexion tests on physical examination [36, 37].

A recent systematic review on the effect of acetabular version on outcomes of hip arthroscopy concluded that surgery in patients with acetabular retroversion resulted in no difference in functional outcomes compared with patients with normal acetabular version [38]. The medical literature has controversial results on the influence of

#### **Figure 3.**

*Antero-inferior hip instability. A and B) right hip with anteroinferior instability observed arthroscopically, with decreased anterior sector angle (ASA < 58°) and increased anterior horn angle (AHA > 50°); C and D) right hip with normal anterior acetabular horn morphology, with normal ASA and normal AHA. Reprinted from Hatem et al. Anteroinferior hip instability in flexion during dynamic arthroscopic examination is associated with abnormal anterior acetabular horn [28].*

#### **Figure 4.**

*Sagittal slice of a hip magnetic resonance arthrogram demonstrating the acetabular slope. (A) Hip with decreased acetabular slope (8°); B) hip with increased acetabular slope (33°). Reprinted from Hatem et al. spinopelvic parameters do not predict the sagittal orientation of the acetabulum [29].*

femoral torsion on hip arthroscopy results. Fabricant et al. observed less improvement following hip arthroscopy in patients with <5° of femoral torsion compared with patients with normal and increased femoral torsion [39]. In contrast, two studies did not report decreased femoral torsion to be a negative prognostic factor for hip arthroscopy [40, 41]. Both studies did not include functional assessment of lumbar spine. Chaharbakhshi et al. reported that patients with combined borderline dysplasia and femoral torsion ≥20° demonstrated significant improvements after hip arthroscopy, despite the inferior results when compared with a control group with normal version and acetabular coverage [42]. Jackson et al. found that femoral torsion >18° was not a negative prognostic factor for hip arthroscopy [43]. Fabricant et al. described inferior results (modified Harris Hip Score) of hip arthroscopy with psoas tenotomy for patients with >25° of femoral torsion [44]. Part of the controversy on the results is explained by differences on how to measure femoral torsion among the studies and the definition of normal, increased or decreased femoral torsion. Most studies on the effect of femoral torsion on hip arthroscopy consider decreased femoral torsion as <5° and increased femoral torsion as >20° [38]. The method utilized for the measurement of the femoral torsion is to be considered for the purpose of comparison to other studies [45–47]. Increasing values for femoral torsion are observed by measuring the femoral neck orientation more distally, and differences of 10° or more among the methods are particularly frequent in patients with excessive femoral torsion [46]. Until the controversy is resolved, it is recommendable to assess femoral torsion and acetabular version for McKibbin's index as routine for patients with hip symptoms.

Femoral derotation osteotomy is to be considered for patients with abnormal femoral torsion, particularly those with failed hip arthroscopy and with low back pain. Tönnis and Heinecke reported satisfactory results of PFDO in 17 patients with decreased femoral torsion and painful hip joints [31]. Another study showing improvement in hip function with PFDO was published by Buly et al., who reported a mean improvement of 27 points in the mHHS following 55 derotation osteotomies in 43 patients [48]. Hatem et al. reported 34 patients who underwent proximal femoral

*Decision Making in Borderline Cases between Hip Preservation and Reconstruction Surgery DOI: http://dx.doi.org/10.5772/intechopen.104765*

derotation osteotomy [37]. Improvement in the mHHS above the minimum clinically important difference (MCID) was observed in 33 hips (89%). In a subgroup of 14 consecutive patients assessed with Oswestry disability index (ODI), the ODI improved from a mean of 45% before the PFDO to 22% at final follow-up [37].

The orthopedic surgeon might consider that extreme values of femoral torsion will have higher biomechanical effects. Therefore, the influence of femoral torsion >30° or below 0° is more clinically significant than the normal range values presented in medical literature. Ligamentous structures play a role on the biomechanical effects of increased and decreased femoral torsion and further studies are needed to better understand the relationship between the iliofemoral ligament and femoral torsion. The patient body habitus and frame will have an influence on strain tolerance to abnormal femoral torsion. Physical examination is essential to determine the biomechanical effects of abnormal femoral torsion and to guide treatment, particularly testing gait in different hip rotation and the hip spine-extension test (**Figure 5**) [49]. The femoral torsion should be considered factor when deciding between hip preservation surgery and THA. In older patients, abnormal femoral torsion may add up to other negative prognostic factors towards a recommendation for THA.

#### **4.3 Ischiofemoral impingement**

Ischiofemoral impingement is associated with limitation in hip extension. A more aggressive treatment approach may be recommended for individuals with secondary biomechanical effects of ischiofemoral impingement as low back and pelvic pain. Gómez-Hoyos et al. simulated a hip extension deficit with an ischiofemoral impingement model to evaluate a primary hip-spine effect due to the limited terminal hip extension produced by the hip pathology [50]. Resultant data described significant increase in lumbar facet joint loading during the impingement state, as compared to the native state for L3-L4 and L4-L5 spine segments. An average 30% increase in facet joint overload was observed between impinged state and native state [50].

Conservative treatment for ischiofemoral impingement includes avoidance of impingement positions, correction of leg length inequality, abductor strengthening, correction of foot hyperpronation and guided injections. Surgical treatment options are indicated when conservative treatment is insufficient: endoscopic lesser trochanter plasty and resection; open lesser trochanter resection; ischioplasty; distal transfer of the lesser trochanter; proximal femoral osteotomy -varus and derotation osteotomy; and finally total hip arthroplasty. The orthopedic surgeon should consider the presence of ischiofemoral impingement in borderline cases between hip preservation surgery and THA. Individuals with ischiofemoral impingement and associated advanced chondral damage of the hip joint are better suited for THA. Total hip arthroplasty is also an alternative to address ischiofemoral impingement in hips with mechanical failure from multiple biomechanical abnormalities, including hip dysplasia and abnormal femoral torsion. A posterior approach allows the repair of hamstring avulsion at the ischial tuberosity, often observed as a result from the ischiofemoral impingement. The presence of contra-lateral hip disease, knee osteoarthritis, and lumbar spine abnormalities reinforce the indication of total hip arthroplasty to treat ischiofemoral impingement. The orthopedic surgeon performing a hip joint replacement in individuals with IFI must be aware of all parameters in the coronal, axial and sagittal planes for the correction of all biomechanical abnormalities. Testing hip extension intra-operatively is fundamental in patients with IFI undergoing total hip arthroplasty through either anterior, lateral or posterior approach.

(A)

(B) (C)

(D) (E)

#### **Figure 5.**

*Hip-spine extension test. (A) the examined hip is brought into terminal hip extension in neutral abduction and rotation while the examiner observes the pelvis and lumbar spine; (B) a positive result is the recreation of low back pain with associated pelvic and lumbar movement in adaptation to the limited hip extension; (C) adding abduction to extension allows the hip to extend without secondary effects at the pelvis and lumbar spine in patients with ischiofemoral impingement; (D) adding internal rotation gives clearance for the extension of the hip in cases of increased femoral anteversion. Conversely, due to premature coupling, internal rotation increases the lumbar and pelvic accommodation in hips with decreased femoral version or retroversion; (E) adding external rotation gives clearance for the extension of the hip in cases of decreased femoral anteversion or retroversion. Conversely, due to premature coupling, external rotation increases the lumbar and pelvic accommodation in hips with increased femoral anteversion.*

*Decision Making in Borderline Cases between Hip Preservation and Reconstruction Surgery DOI: http://dx.doi.org/10.5772/intechopen.104765*
