**2. Degree of chondral damage**

The degree of chondral damage is the first element to consider in borderline cases between hip preservation and reconstruction surgery. The results of hip preservation surgery are inferior in individuals with more advanced chondral disease [1]. The

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

degree of chondral damage observed at the time of surgery is associated with risk of conversion to THA after hip arthroscopy. McCarthy et al. reported the likelihood of THA at a mean follow-up of 13 years after hip arthroscopy according to the cartilage disease observed arthroscopically [2]. Femoral head chondral damage was the strongest risk factor for conversion to THA. Hips with Outerbridge Grades III-IV disease at the femoral head were 58 times more likely to require conversion to THA when compared to Outerbridge Grades 0–2 [2]. Hips with acetabular cartilage disease Grade II-IV were 20 times more likely to require conversion to THA when compared to Outerbridge Grades 0–1. For patients who underwent THA, McCarthy et al. reported an average time of 4.8 years between the hip arthroscopy and THA [2]. Horisberger et al. reported the rate of conversion to THA in 20 patients with generalized degenerative changes at the hip joint observed during arthroscopy [3]. From 20 patients, 50% had undergone or planned to undergo a THA at a mean follow-up of 3 years. The mean time between the hip arthroscopy and THA was 1.4 years [3].

Preoperative imaging studies are helpful to estimate the risk of conversion to THA after hip preservation surgery [3, 4]. Hip joint space measurements on standing and supine pelvic radiographs have been shown to be equivalent by Bessa et al. [5]. Philippon et al. described that hips with joint space <2 mm at pre-operative radiograph were 39 times more likely to progress to a THA than those with ≥2 mm of joint space [6]. Larson et al. reported that 82% of the individuals with pre-operative joint space narrowing (>50% joint space narrowing compared to contra-lateral normal hip or ≤ 2 mm of joint space) failed to improve above 70 points on Harris Hip Score or underwent THA at a mean follow-up of 27 months. Zimmerer et al. studied the 11-year hip survivorship in 112 patients after primary hip arthroscopy according to the pre-operative Tönnis grade [4]. Conversion to THA was observed in 54% of the hips with Tönnis 2 or 3. In contrast, 14% of hips with no or minimal osteoarthritic changes on radiographs (Tönnis 0 or 1) underwent a THA following the primary hip arthroscopy at a mean follow-up of 11 years [4]. Modern techniques of labral repair may affect previously reported outcomes and need further studies.

Despite the usefulness of pre-operative imaging to estimate the degree of chondral damage, conventional radiographs and magnetic resonance imaging (MRI) underestimate the severity of chondral disease in 3 out of 4 patients with marked generalized chondral lesions [3]. For hips with more than 2 mm of joint space or Tönnis grade 0 and 1, Rosinsky et al. reported that narrower joint space was not correlated with intraoperative cartilage damage (**Figure 1**) [7]. The authors mentioned that narrower joint space (above 2 mm) may be an anatomic variant and cannot predict actual intraoperative cartilage damage [7].

The frequent conversion to THA after hip preservation surgery in hips with advanced acetabular chondral damage at long term does not mean patients cannot benefit from hip preservation at short and mid-term. Peters et al. reported improved Harris hip scores from an average of 68 preoperatively to 91 at a mean follow-up of 26 months after open treatment for femoroacetabular impingement in 39 hips with Outerbridge grade 4 acetabular chondral damage [8]. Despite the good clinical outcomes, the authors described radiographic progression of osteoarthritis in 43% of the hips with Outerbridge grade 4 acetabular chondral damage [8]. The above paper reinforces that functional and clinical assessment are essential in association to radiographic evaluation when making clinical decisions for patients with degenerative changes at the hip. The effects of limited hip mobility on the lumbar spine and pelvis also need to be considered and will be discussed later in this chapter (**Figure 2**).

#### **Figure 1.**

*Imaging of a 67-year-old patient who was recommended total hip arthroplasty 1 year after hip arthroscopy. Femoral head chondral damage observed arthroscopically, despite preserved joint space pre-operatively. Figures A, B and C) radiographs demonstrating joint congruency and preserved joint space; D) arthroscopic image demonstrating the chondral damage at the femoral head (arrows); E and F) 10 months post-operative radiographs demonstrating lateral migration of the femoral head (yellow line) and subtle narrowing of the joint space; G and H) 10 months post-operative magnetic resonance imaging demonstrating the chondral damage with subchondral edema, not observed in the pre-operative MRI.*

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

#### **Figure 2.**

*Anteroposterior and lateral radiographs of a 53 years-old female with advanced left hip osteoarthritis and four years of conservative management including anti-inflammatory medication and intra-articular injection with corticosteroid. Modified Harris hip scores for the left hip is 93.5 out of 100.1. In contrast to the very satisfactory right Harris hip score, the Oswestry lumbar disability score has worsened from 8 to 16% in one year. This patient illustrates the importance of clinical assessment in association to imaging studies, as well as the effects of decreased hip mobility at the lumbar spine, when making clinical decisions for patients with hip diseases.*

Hips with cam femoroacetabular impingement and advanced chondral damage often progress with anterosuperior migration of the femoral head to the cartilage defect. This finding has been recognized as a landmark for progressive osteoarthritic changes [9]. The anterosuperior migration of the femoral head is usually not evident on the anteroposterior or lateral radiographs. False profile of Lequesne radiographs and magnetic resonance are fundamental to identify the anterosuperior migration of the femoral head to the cartilage defect. The authors of the current chapter believe the migration of femoral head is a turning point on the progression of femoroacetabular impingement to be considered when recommending a hip preservation surgery. Hips with cam morphology and anterosuperior migration of the femoral head to the chondral defect are under the risk of further instability and rapid progression of osteoarthritis if undergoing a hip preservation surgery.
