Clinical Outcomes of Revision Hip Arthroscopy for Synovial Chondromatosis

Background: Synovial chondromatosis (SC) is a relatively rare disease and there were few studies on causes and clinical outcomes of revision surgery for SC. The purpose of this study was to evaluate clinical outcomes of revision hip arthroscopy for synovial chondromatosis. Methods: We evaluated consecutive patients who underwent revision hip arthroscopy for SC in our hospital between January 2008 and January 2020. Radiographic evaluation was made before and after surgery. Preoperative patient-reported outcomes (PROs) and PROs at nal follow-up were obtained, including visual analog scale (VAS) for pain, the International Hip Outcome Tool-12 (iHOT-12) and modied Harris Hip Score (mHHS). Results: A total of 8 patients (mean age, 39.5 years; age range, 27-62 years; 5 males and 3 females) were included in this study. The recurrence rate of hip SC in our hospital was 6.8%. The average follow-up period after surgery was 47.3 months (range, 12–120 months). Before surgery, mean mHHS was 60.6±17.3 (range, 20-77), mean iHOT-12 was 43.8±13.7 (range, 18-69), and mean VAS was 3.1±1.7 (range, 1-7). At the nal post-operative follow-up, mean mHHS was 83.8±16.6 (range, 43-91), iHOT-12 was 80.6±19.7 (range, 32-90), and mean VAS was 0.6±1.8 (range, 0-5). All results demonstrated statistically signicant improvement (P < 0.05). Recurrence of SC was found in 2 patients 1 year and 4 years after revision hip arthroscopy, respectively. Conclusion: Hip arthroscopy had good clinical outcomes for revision surgery of SC.


Patients
We evaluated consecutive patients who underwent revision hip arthroscopy for SC in our hospital between January 2008 and January 2020. The inclusion criteria were as follows: (1) patients were diagnosed with SC and underwent primary hip arthroscopy for SC in our hospital or other hospitals; and (2) underwent revision hip arthroscopy because of unrelieved symptoms or limited range of motion (ROM). Patients who could not complete the clinical follow-up were excluded from the study. All participants signed informed consent. The study was approved by an institutional review board.
Physical examination and radiographic assessment All patients underwent a systematic physical examination. Flexion, adduction, and internal rotation (FADIR) or exion abduction external rotation (FABER) tests are considered positive if hip or groin pain was elicited when the hip was placed in 90° of exion and then adduction and internal rotation or exion, abduction and external rotation applied. [15] Supine anteroposterior hip radiographs, cross-table lateral radiographs, CT images, and MR images were obtained for all patients preoperatively ( Figure 1). Crosstable lateral radiographs and CT images were obtained for all patients postoperatively. Preoperative alpha angle and lateral center-edge angle (LCEA) were measured as described by previous studies. [16,17] Surgical procedure One surgeon with more than one decade of experience of this procedure performed standard hip joint arthroscopy for all patients. The basic procedure was as described by Zhang et al. [3] For patients with recurrence or remaining loose body, peripheral compartment was explored rstly without joint distraction at 45 degrees of hip exion using 30°-arthroscopes. Most of the recurrent or remaining loose bodies could be removed by lavage, and larger ones could be removed using a grasper. Secondly, traction was applied to the operative extremity and a radiofrequency tool was used to complete capsulotomy. Detailed inspection of the central compartment was undertaken to assess the acetabular rim, acetabular labrum, articular cartilage, and ligamentum teres using 70°-arthroscopes. Removal of loose bodies and synovectomy was done. Articular cartilage lesions of the acetabulum and femoral head were evaluated according to the Outerbridge classi cation. [18] Labral repair or labral debridement was performed according to the nature of injury. If a cam bump in the head-neck junction or acetabular overcoverage was identi ed, femoral osteoplasty or acetabuloplasty was performed. Finally, the hip was moved into 45° of exion and various degrees of rotation for thorough inspection of the peripheral compartment again after traction release. Revision surgery was much more di cult than primary surgery. The most common sites of remaining or recurrent SC were medial joint recess, posterior capsule, and acetabular fossa. These areas could be treated to the greatest extent by using curved shaver, curved nucleus pulposus forceps at the position of internal and external rotation under hip exion.

Outcomes evaluation
Preoperative patient-reported outcomes (PROs) and PROs at nal follow-up were obtained, including visual analog scale (VAS) for pain, the International Hip Outcome Tool-12 (iHOT-12) and modi ed Harris Hip Score (mHHS). Complications or revision hip arthroscopy were recorded.

Statistics
The two-tailed paired t test was used to evaluate signi cance between preoperative and postoperative PROs. P values <.05 were considered statistically signi cant. All statistical analyses were performed with SPSS Statistics, version 22 (IBM).

Results
During the study period, a total of 74 patients underwent hip arthroscopy for SC in our hospital. Eight patients underwent revision hip arthroscopy during this time. Five patients underwent primary hip arthroscopy in our hospital and 3 patients underwent primary surgery in the other hospitals. The recurrence rate of hip SC in our hospital was 6.8%. As shown in Table 1 [1,10,14] The recurrence rate in our hospital was 6.8%, which was similar to what Darren et al. [10] reported. Boyer and Dorfmann evaluated outcomes in 69 patients treated with arthroscopy alone, of whom 51 required no further treatment and 18 required further arthroscopies. [14] Of these 18 patients, eight had an excellent outcome, nine had a good outcome, and the treatment failed in one. Lee et al. [1] reported recurrence in 4 of 24 patients who underwent hip arthroscopy for SC and these 4 patients underwent revision arthroscopy. SC recurred again in 1 of the 4 cases and a third surgery was performed. Ferro et al. [8] reported 1 patients who underwent two revision surgeries after primary hip arthroscopy for SC and nally underwent total hip replacement 4 years after the initial hip arthroscopy. Zhang et al. [3] reported 2 patients underwent revision arthroscopy because of adhesions within the hip or recurrent SC. Several revision hip arthroscopies for SC had been reported. However, the clinical outcomes of revision arthroscopy were quite different and current studies did not have detailed clinical follow-up. We evaluated consecutive patients who underwent revision hip arthroscopy for SC in our hospital and proved that that hip arthroscopy had good clinical outcomes for revision surgery of SC. The mean time between primary surgery and revision surgery was 30.8 months (range, 4-96 months) in this study. Lee et al. reported the average period between the rst surgery and recurrence was 3.2 years (range, 0.8-3.8 years). [1] Boyer et al. reported the mean time between the rst and second arthroscopies was three years. [14] The time between primary surgery and revision surgery of the three studies was similar.
According to the current researches, the main causes for revision arthroscopy were recurrent SC and adhesion. In this study, 7 patients underwent revision surgery because of recurrent SC, 2 patients underwent revision surgery because of adhesion and one because of remaining loose bodies. One of the two patients with adhesion had recurrent SC and we thought recurrent SC may be the reason of adhesion. One patient did not achieve good clinical results. Her mHHS improved from 20 preoperatively to 43 postoperatively and iHOT-12 improved from 18 preoperatively to 32 postoperatively. VAS improved from 7 to 5. Recurrence of SC was found 4 years after revision arthroscopy. At nal follow-up, range of motion of this patient improved, but the symptoms did not improve much. Recurrence of SC was found in 2 patients 1 year and 4 years after revision hip arthroscopy, respectively. Lee et al. [1] reported that the symptomatic SC recurred in 4 of 24 cases who underwent hip arthroscopy and symptomatic disease recurred again in 1 of the 4 cases, and thus, a third surgery was performed. The condition of the patient who underwent the third surgery was exacerbated because of adhesions resulting from extensive intrajoint synovectomy, and the range of motion of the hip joint was decreased after surgery compared with the patient's condition before surgery. [1] Ferro et al. [8] reported 1 patients who underwent two revision surgeries for SC and nally underwent total hip replacement 4 years after the initial hip arthroscopy. In this study, the two patients who had recurrence of SC after revision arthroscopy did not accept third surgery. SC tends to recur whether after primary surgery or revision surgery. It should be mentioned that one patient in this study underwent hip arthroscopy for SC as primary surgery and underwent open surgery for recurrent SC as the second surgery in another hospital. This patient underwent hip arthroscopy for SC as the third surgery in our hospital. This patient had serious recurrence after second open surgery and the SC expanded along the incision and some even grew to obturator externus muscle, which made the third arthroscopy surgery so di cult that it was impossible to remove SC completely (Fig. 2). This patient was satis ed with the outcomes of third arthroscopy surgery. At one-year follow-up, this patient had no obvious discomfort and could walk and live normally. He felt a little discomfort only when the hip exion angle was more than 110 degrees.
It should be noticed that 4 in 8 patients who underwent revision arthroscopy had combined FAI. Such a high rate of combined FAI may be related to repeated stimulation of SC. The association between FAI and SC has been reported previously by Padhy et al. in 2009, who described a case of FAI accompanied by SC. [20] Abolghasemian et al. proposed that SC can induce changes compatible with typical cam-type FAI, and that this can represent another mechanism leading to hip osteoarthritis in patients with SC. [21] The presence of unilateral cam-type impingement can be a clue to a possible diagnosis of underlying SC. [21] This study had several limitations. First, the sample size of this study was small. However, the patients who underwent revision arthroscopy for SC was scarce. Second, the time of follow-up ranged from 12 months to 120 months. One patient had a relatively short follow-up.
In conclusion, hip arthroscopy had good clinical outcomes for revision surgery of SC.