Pigmented villonodular synovitis does not influence the outcome following cementless total hip arthroplasty using ceramic-on-ceramic articulation: a case-control study with middle-term follow-up

Pigmented villonodular synovitis (PVNS) of the hip is a benign, but potentially locally aggressive and recurrent monoarticular disorder which typically affects large joints; 80% of the time it involves the knee, while hips are affected only 15% of the time [1]. It is an uncommon disorder, with an estimated incidence of 1.8 per million patients [2‐4]. It is characterized by a proliferation of synovial villi and nodules within joint spaces, bursa, or tendon sheaths [5]. As synovial hyperplasia pervades the hip, it causes discomfort by narrowing the joint space, leading to sharp hip pain [3]. A radical synovectomy, whether via arthroscopy or an open surgical approach, has been utilized as a treatment for hips with mild cartilage degeneration. However, in cases demonstrating severe end-stage arthritis due to disease progression, total hip arthroplasty (THA) plus radical synovectomy is the preferred treatment choice [6].

PVNS of the hip commonly affects patients in their third or fourth decade of life [7]. A recent study reported that complications and revision rates following THA are high in patients with PVNS due to the youth of patients and the utilization of conventional polyethylene [8]. Given the likelihood of requiring revision surgery for younger patients undergoing THA, the concern of implant survivorship, wear performance, and functionality should be considered when selecting a fixation technique and a bearing surface. As one of the most popular combinations, cementless implants with ceramic-on-ceramic (CoC) articulation have shown potential benefits in young patients, as they have low wear rates with excellent clinical outcomes [9‐13]. Although several studies have suggested acceptable outcomes with a low recurrence rate following THA in PVNS patients during the long-term follow-up [1, 6, 8, 14], there is a paucity of data focusing on cementless implants using CoC articulation in these patients. Moreover, these previous studies were limited by small sample sizes and lacked a control group in their evaluation of outcomes.

Therefore, the purpose of this study was to investigate the disease recurrence rate and the treatment outcomes including Harris Hip Scores, complications, and revision rates following cementless THA with CoC articulation in patients with PVNS.

This study demonstrated that patients with PVNS undergoing cementless CoC THA had similar survivorship and functionality compared to those with the diagnosis of osteonecrosis of femoral heads or osteoarthritis of hips. None of the patients with PVNS experienced infection, osteolysis, dislocation, or ceramic fracture after a mean follow-up of 8.6 years. Moreover, there was no evidence of recurrent PVNS during the middle-term follow-up in the present study.

PVNS is a proliferative disorder characterized by infiltration of hemosiderin-laden macrophages, multinucleated giant cells, and inflammatory cells which carry a high risk of recurrence [22‐24]. Due to its low incidence, PVNS is not well understood. While a consensus regarding the pathogenesis of PVNS has not yet been established, some researchers have hypothesized that trauma-induced hemorrhage could be a causative factor [25, 26]; in previously published case series, prior trauma ranged from 3 to 53% [27] In our study, 4 of 19 patients with PVNS (21.1%) had had a history of hip trauma before the diagnosis of PVNS. Although other researchers suggested patients with PVNS commonly have abnormal serum inflammation markers [28], there were only two patients with PVNS (10.5%) with elevated ESR and CRP in our study. However, our results correspond to those reported by Gitelis et al. who initially documented a lack of an inflammatory syndrome associated with PVNS [27].

Despite improved imaging, definitive preoperative diagnosis of PVNS is difficult without histopathology. At the early stage of PVNS, the treatment primarily includes either open or arthroscopic synovectomy. However, PVNS has a high recurrence rate, up to 25%, likely due to incomplete debridement without neck cutting [2]. In the present study, five patients with PVNS had undergone previous arthroscopic synovectomy; the duration between the last synovectomy and the primary THA were 0.8, 2, 2.5, 3.1, and 3.6 years (mean 2.4 years). We hypothesize that the short-term recurrence may be related to incomplete synovectomy by arthroscopy technique.

At end-stage PVNS, THA is the most effective treatment option, with lower PVNS recurrence rates and lower revision rates than synovectomy alone [8]. The lifespan of the primary THA is of significant concern, as patients with PVNS are typically younger and will therefore retain the implants for a longer duration of time. The two most important aspects of implant longevity are the method of implant fixation and the type of bearing surface [14]. While case studies of PVNS of the hip are limited, both cemented and cementless THA have been reported to result in good outcomes [14].

No recurrent PVNS was found during the follow-up in the present study, which is similar to prior studies [5, 7, 13, 14]. Yoo et al. [5] reported eight PVNS patients with cementless THA and none of the patients had clinical or radiographic evidence of recurrent PVNS for an average of 8.9 years follow-up. Recently, Tibbo et al. [7] reviewed 25 patients PVNS who underwent THA with conventional polyethylene or highly crosslinked polyethylene bearings during a mean of 10 years follow-up. Of them, only one patient (4%, 1/25) occurred recurrence at 24 years postoperatively.

Of the studies involving cementless THAs, most of the studies, however, only reported on polyethylene or metal bearing surfaces [5, 7, 14, 27]. Hoberg et al. [29] reported two cases of metal-on-metal hip resurfacing in patients with PVNS. Yoo et al. [6] described revisions due to prosthesis loosening and osteolysis in two of eight patients who had undergone THA using metal-non-cross-linked polyethylene bearing and periprosthetic osteolysis; additionally, two other patients had loosening with zirconia-non-cross-linked polyethylene. The need for revisions and the shorter implant survivorship in these cases is thought to be due to conventional polyethylene induced-wear and metal ion-induced osteolysis resulting in aseptic loosening [28, 29]. Recently, Tibbo et al. reported the 10-year survivorship free from any revision was 100% for highly crosslinked polyethylene liners and 66% for conventional polyethylene liners [8]. The Ceramic-on-ceramic bearing surface, characterized by its superior hardness and smoothness, has the lowest wear rates in comparison to all other bearing surfaces in THA [30, 31]. In our study, only one patient underwent a revision arthroplasty due to aseptic loosening. The 10-year implant survivorship free of any revision after CoC THA was 90.0% in the PVNS group, which was similar to that in the control group (92.5%, p = 0.99). Moreover, we did not identify any local recurrence in the PVNS cohort.

There are several limitations in our study. A major limitation was the retrospective case-control design of the study, which is subject to inherent biases of the design. Additionally, we did not sort the disease manifestations (diffuse vs. focal) based on pathological classification, although all cases were diagnosed by histological evaluations. Another limitation is that we cannot compare outcomes of different bearing surfaces, such as metal-on-metal, metal-on-polyethylene, or ceramic-on-polyethylene articulation, as PVNS patients in this study were all treated with CoC THA.

In conclusion, end-stage PVNS of hip treated with cementless CoC THA had a low complication rate with similar implant survivorship and restoration of function in comparison to other young patients with osteonecrosis or osteoarthritis. These findings indicate that utilization of cementless THA ceramic-on-ceramic bearings could be a viable option for young patients with PVNS.