Proximal fibular osteotomy relieves pain in spontaneous osteonecrosis of the knee: A retrospective study

Abstract

Spontaneous osteonecrosis of the knee (SONK) causes knee pain and joint motion limitation. Ischemia or insufficiency fracture may be the cause, but no consensus has been developed. Proximal fibular osteotomy (PFO) has been reported to relieve pain from osteoarthritis through medial compartment decompression. We reviewed the effect of this procedure on medial compartment SONK patients and explored clinical and radiological results. Since January 2018 to January 2020, the data of 12 knees (8 right and 4 left) from 11 SONK patients (9 women and 2 men) who received PFO were analyzed. The average age was 61.5 years. The diagnosis of SONK was established through weight-bearing anterior-posterior radiographs or magnetic resonance imaging (MRI). Visual analog scale (VAS) scores, Oxford knee score (OKS), Femorotibial angle (FTA), medial joint space, and lateral joint space were documented preoperatively and at follow up visits. Outcome assessment for the clinical and radiographic data was reviewed at 12- and 24-month follow-up visits. The mean follow up period was 33 months. All patients were able to walk with or without cane assistance the day after surgery. Both VAS score and OKS (preoperative: 6.6 ± 0.9 and 24.7 ± 3.8, respectively) improved significantly at the 12-month follow-up, and to 24-month follow-up (3.6 ± 1.3 and 35.6 ± 4.5, respectively, P < .05). Medial joint space ratio increased from 0.36 to 0.50 (P < .05). Changes of FTA were insignificant at any point of follow up. Four patients underwent follow-up MRI, and a decrease in the osteonecrotic area was clearly observed in 2 patients. By achieving medial knee decompression, PFO allowed quick weight-bearing recovery, pain relief, and improvement in knee function in SONK patients.

Figure 1.

STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) flow chart of study participants.

Figure 2.

Preoperative MRI of a 50-year-old woman showing (A) a hyperintense signal on T2-weighted image on coronal view and (B) a hypointense signal on T1-weighted image at the medial femoral condyle on sagittal view.

Figure 3.

Preoperative and 12- and 24-month follow-up VAS scores.

Figure 4.

Preoperative and 12- and 24-month OKS.

Figure 5.

(A) A 61-year-old man with spontaneous osteonecrosis of the medial femoral condyle. (B) Postoperative radiograph showing increased medial compartment space and a decrease in the SONK radiolucent area.

Figure 6.

A 51-year-old woman who received right knee PFO surgery due to SONK. Coronal and axial MRI revealed a large hyperintense area on the T2-weighted image (A) and hypointense area on the T1-weighted image (C). Significant reduction of the osteonecrotic area after surgery on T1- (B) and T2-weighted images (D).

Figure 7.

(A) Symmetric load on medial and lateral knee compartment, with stronger support in the lateral compartment due to additional fibular support. (B) With age, medial knee support weakens more than the lateral support because of a decreased tibial cortical bone area but nearly unchanged lateral fibular support. This nonuniform settlement results in load medialization and a net varus force. (C) After proximal fibular osteotomy, lateral fibular support is disrupted. Weight load can settle on the lateral side, reaching a more symmetric load distribution.