Quinten Rikken

Summary in English

Part 1. Introduction
Chapter 1 provides a general introduction into the etiology, epidemiology, clinical presentation, and treatment of osteochondral lesions (OCLs) of the ankle. As no gold-standard treatment has yet been identified for the treatment of ankle OCLs controversy remains on its optimal management. The main goal of this thesis was to improve the evidence-based treatment algorithm for patients with an OCL of the ankle. This thesis aimed to do so by evaluating existing treatment strategies and aimed to identify factors for patient selection. The focus of this thesis was on bone marrow stimulation and fixation for osteochondral lesions of the talus (OLT), and the treatment of osteochondral lesions of the tibial plafond (OLTP).

Part 2. Bone Marrow Stimulation for Osteochondral Lesions of the Talus
Bone marrow stimulation (BMS) is the most common surgical treatment for osteochondral lesions of the talus. While successful in 4 out of 5 patients up-to mid-term follow-up, less is known about its long-term clinical sustainability. Previous studies have cited the inferior wear characteristics of the substitute fibrocartilage, which is formed after BMS, as a reason for an increased risk of long-term issues, such as recurrent complaints, the (early) onset of osteoarthritis, and revision surgery.

Chapter 2 evaluates the current literature on the long-term clinical and radiological outcomes following arthroscopic BMS. We observed 323 ankles reported in 6 studies at a mean 13-year follow-up. As a pooled aggregate, it was observed that the American Orthopaedic Foot and Ankle Society (AOFAS) score at final follow-up was 84 out of 100 points, that 78% of patients participated in any level of sports, and that revision surgery occurred in 7% of cases. However, progression of degenerative changes was observed in 28% of ankles, with only a few cases of joint space narrowing or end-stage osteoarthritis. Notably, the quality of the literature was low- to moderate and included a heterogenous patient population. In chapter 3 we conducted a survival analysis (free from revision surgery) for 262 patients that underwent arthroscopic BMS at a minimum 10-years follow-up. The 10-year cumulative survival rate was 82%. At 15 years of follow-up the survival rate was 82%. The median time to revision was 2.4 years. As a secondary analysis we analyzed if baseline patient- and lesion factors were associated with survival outcomes. It was found that obesity (a body mass index ≥ 30 kg/m2) was associated with poorer survival. This factor should be incorporated into the treatment algorithm for patients with an OLT when counseling for surgery.

Another controversy regarding BMS is whether patients can benefit from repeating the surgery. The current evidence is poor and shows mixed results, while selecting the right patients for such a procedure could lower costs and shield patients from more invasive surgery. In the study described in chapter 4, patients with a non-primary OLT were matched to a primary OLT in a 1:2 ratio, and 1-year clinical outcomes were compared. 11 patients with a non-primary OLT were matched to 22 patients with a primary OLT. It was found that there were no significant differences between the groups in pain outcomes, functional outcomes, quality of life, return to sports and work, or lesion filling on 1-year CT. Chapter 5 describes a prospective 2-year follow-up cohort of patients that underwent arthroscopic BMS. The aim was to assess the 2-year postoperative clinical outcomes in 19 patients with a non-primary OLT and compare these to 25 patients with a primary lesion. It was observed that both groups had a significant improvement in patient-reported pain and functional outcomes compared to baseline. However, patients with a non-primary OLT had less favorable improvements compared to primary BMS. Moreover, non-primary BMS did not result in a statistically significant higher revision rate compared to primary BMS.

Part 3. Fixation for Osteochondral Lesions of the Talus
Fixation for symptomatic OLT with an osteochondral fragment can be regarded as the current gold-standard treatment for such lesions as 9 out of 10 patients achieve a clinically successful outcome and union of the fragment. The procedure can be performed open or arthroscopically. For patients with a chronic lesion, which can be seen as an intra-articular non-union, the Lift-Drill-Fill-Fix (LDFF) technique was developed. Though the arthroscopic approach of the LDFF showed good early- to mid-term results, no studies have been conducted on the safety and clinical outcomes of open LDFF. Additionally, it remains to be elucidated what the long-term outcomes of arthroscopic LDFF are. As such, this thesis aimed to fill these research gaps.

Chapter 6 describes the step-to-step surgical technique of the open LDFF procedure. Moreover, the study provides an insight in the initial prospective results of the cohort, which were found to be promising. Chapter 7 focused on the 2-year prospective patient-reported clinical outcomes and 1-year fragment union rate in 34 patients following open LDFF for chronic OLT with an osteochondral fragment. Patients reported significant improvements in pain, function, and a quality-of-life subscale. The fragment union rate was 91%, while its was found that obesity was associated with non-union. During the study period, 3 revision surgeries were performed for a symptomatic non-union of the fragment and 2 complications occurred. It was concluded that open LDFF leads to excellent 2-year outcomes and is a viable treatment for fragmentous OLT, while obesity may pose a risk for non-union of the fragment, and patients should be counseled accordingly.

Chapter 8 describes the long-term results of arthroscopic LDFF from a historic cohort consisting of 20 ankles (18 patients), which were evaluated at a mean 7-year follow-up. We observed that the patient-reported outcomes (which included reported pain, functional ability, and quality of life) remained stable over time, and that the survival free from revision surgery rate was 87% (18/20 ankles). Arthroscopic LDFF, therefore, seems to result in sustained long-term outcomes.

Part 4. Management of Osteochondral Lesions of the Tibial Plafond
Osteochondral lesions of the tibial plafond are located opposite to the talus and are considered rare. Treatment strategies for these lesions are largely copied from their use in talar lesions and lack patient- or lesion factors to guide management. The management of OLTP is therefore an open question, with outcomes reported in small and low-evidence case-series, without any evidence on non-operative treatment. This clear lack of evidence leads us to come up with the first steps towards an evidence-based treatment approach for OLTP in order to improve outcomes for our patients.

Chapter 9 summarizes the current literature on management of OLTP. No studies describing non-operative treatment were found. Six different surgical treatment options were among the 10 included studies (175 patients) with BMS being the most frequently reported among these. The patient-reported outcomes of surgical treatment for OLTP were considered moderate to good, while complications and reoperations were rarely reported. Moreover, the quality of evidence was considered low, and there was considerable underreporting of clinical, radiological, and sport outcomes, amongst a heterogenous patient population.

In chapter 10 a 2-year prospective study among 18 patients who underwent non-operative management for a symptomatic OLTP assessed its safety and efficacy. Patient-reported outcomes, follow-up CT-scans, and conversion to surgery or any complications were assessed. No significant improvement of the primary outcome, the NRS during weightbearing, was observed. Similarly, no significant changes in the other NRS scales (in rest, during running, and stairclimbing), the FAOS functional outcome score, and SF-36 general health questionnaire were observed. CT-evaluation of 13 available cases showed that lesion size and volume did not change compared to baseline. In 10 (77%) cases signs of lesion filling or no change was found. 9 out of 10 patients returned to sports at any level and work. No complications and 1 case of conversion to surgery was observed. These results suggest that non-operative management for OLTP appears safe but yields marginal improvements in patient-reported pain and functional outcomes.

Chapter 11 describes a retrospective cross-sectional study of 51 patients who underwent arthroscopic BMS for OLTP at 2 to 22 years follow-up. We observed that pain outcomes and functional outcomes were good, but that patients reported higher levels of pain during running. Lesion size was found to correlate with worse pain scores. We did not find a coexisting talar lesion to influence outcomes in this cohort. Additionally, there was a low rate of revision surgeries and complications. These results point to favorable outcomes following BMS for OLTP in activities of daily living, but less so in more strenuous activities. Lesion size may be a factor to take in consideration when treating OLTP with BMS, though further studies should confirm this and determine a cut-off size.

Chapter 12 is a surgical technique study for a novel treatment of large medial and central OLTP, by means of an osteotomy directly transecting the lesion and filling it with autologous bone. This technique adds a new treatment layer for challenging and/or recurring OLTP. The safety and clinical efficacy will have to be investigated in future studies to validate the procedure.

Part 5. Discussion
In this section the findings of this thesis are discussed and compared to the literature. The discussion section provides clinical recommendations based on the work from this thesis. These recommendations are visualized in a treatment algorithm flow-chart.