A novel osteotomy tool reduces complications and improves operative efficiency in proximal fibular osteotomy for medial compartment knee osteoarthritis: a retrospective comparative study

Abstract

Background

Proximal fibular osteotomy (PFO) is a surgical treatment for medial knee osteoarthritis (MKOA). This study aimed to evaluate the safety and efficacy of a novel instrument, the Threading Saw Pliers, compared to conventional techniques in performing PFO.

Methods

Between February 2021 and February 2023, 80 patients undergoing PFO for MKOA were allocated into two groups based on the chronological introduction of the tool: the Modified group (using Threading Saw Pliers, n = 40) and the Conventional group (n = 40). Operating time, intraoperative blood loss, perioperative complications, Visual Analogue Scale (VAS) score, Knee Society Score (KSS), and Hospital for Special Surgery Knee Score (HSS) were assessed. The follow-up span over a time line of at least 12 months.

Results

Baseline characteristics were similar between the two groups. The Modified group demonstrated a significantly shorter mean operating time (25.14 ± 8.11 vs. 55.33 ± 6.90 min, P < 0.001) and reduced mean blood loss (20.11 ± 30.29 vs. 101.19 ± 29.33 ml, P < 0.001). The overall perioperative complication rate was markedly lower in the Modified group (2.5% vs. 27.5%, P = 0.007). While VAS, KSS, and HSS scores showed significant improvement from preoperative values within each group at 6 and 12 months postoperatively (P < 0.05), there were no significant differences in these clinical outcomes between the two groups at either time point (P > 0.05).

Conclusions

The use of the Threading Saw Pliers in PFO is associated with superior perioperative safety, including reduced operating time, less blood loss, and fewer complications, while achieving equivalent mid-term clinical outcomes compared to conventional techniques. The Threading Saw Plier represents a valuable technical advancement for this procedure.

Introduction

Knee osteoarthritis (KOA) is a prevalent degenerative joint disease causing significant pain and disability [1, 2]. For patients with medial compartment involvement, proximal fibular osteotomy (PFO) has emerged as a simple, pain relieving and effective joint-preserving surgical option [3–5].

Despite its clinical benefits, the technical execution of PFO carries inherent risks due to the complex anatomy around the proximal fibula, particularly the proximity of the common peroneal nerve and peroneal vessels [6]. A variety of osteotomy techniques are currently employed, utilizing instruments such as wire-saws, oscillating-saws, osteotomes, bone rongeurs, and grinding drills [7, 8]. A common drawback among these conventional tools is the lack of integrated protection for surrounding neurovascular structures during the osteotomy process, thereby elevating the risk of iatrogenic injury.

To enhance the safety and reproducibility of PFO, a novel osteotomy tool, the Threading Saw Pliers (Patent No.: ZL201821608507.5), was designed. This instrument was designed to facilitate a safer dissection and controlled passage of a wire saw around the fibula. The purpose of this retrospective study was to compare the perioperative safety and mid-term clinical efficacy after PFO performed using this novel tool versus conventional techniques. It was hypothesized that the modified technique will reduce operating time, blood loss, and complication rates without compromising functional outcomes (Fig. 1).

Fig. 1.

modified proximal fibular osteotomy

Materials and methods

The requirement for informed consent was waived by the Institutional Review Board due to the retrospective design and the use of anonymized clinical data.

Clinical trial arrangement

The 90 patients who underwent PFO for MKOA between February 2021 and February 2023 were screened for eligibility. Patients were allocated into two groups based on the date of surgery: The Modified group initially comprised 40 patients treated for MKOA with PFO using the novel Threading Saw Pliers; The Conventional group comprised 40 patients who underwent PFO using standard techniques (wire saws, osteotomes, rongeurs) prior to the adoption of the new tool. This sequential allocation was used to minimize selection bias and reflect the pragmatic introduction of the new technology.

Inclusion and exclusion criteria

Inclusion criteria: (1) Diagnosis of MKOA according to ACR criteria; (2) Failure of conservative treatment; (3) Underwent unilateral PFO as the primary surgical intervention; (4) Complete medical and follow-up records.

Exclusion criteria: (1) Knee valgus deformity; (2) Concurrent severe medical comorbidities contraindicating surgery (e.g., DVT, infection); (3) History of prior knee or fibular surgery; (4) Lost to follow-up.

The novel osteotomy tool

The Threading Saw Pliers (Fig. 2) are constructed from medical-grade metal. Its key feature is a front-mounted closed-loop channel that allows a wire saw to be passed through it, enabling controlled guidance around the bone while theoretically protecting surrounding soft tissues.

Fig. 2.

The novel osteotomy tool (Threading Saw Pliers)

Patient demographics

Eighty patients were included. The Modified group had 21 males and 19 females with a mean age of 71.29 ± 3.11 years. The Conventional group had 22 males and 18 females with a mean age of 70.98 ± 2.98 years. There were no significant differences in baseline demographics between the two groups (Table 1), indicating well-matched cohorts for comparison.

Table 1.

Comparison of baseline data between groups (x̄ ± s)

Project	Modified group (n = 40)	Traditional group (n = 40)	χ2/t	P
Sex (M/F)	21/19	22/18	0.201	0.654
Age(year)	71.29 ± 3.11	70.98 ± 2.98	0.683	0.495
Weight(kg)	64.33 ± 2.98	64.81 ± 1.88	1.292	0.198
Disease course (years)	11.01 ± 0.11	9.8 ± 0.26	1.008	0.315

Surgical technique

Modified group

The patient was placed in the prone position. A ~ 3–4 cm longitudinal incision was made approximately 5 cm distal to the fibular head. Blunt dissection was performed along the intermuscular space between the peroneus longus/brevis and the soleus to expose the fibula. The Threading Saw Pliers were inserted medially along the bone surface, and a wire saw was threaded through the instrument’s channel, encircling the fibula at the predetermined osteotomy sites (approximately 2 cm apart). The soft tissues were protected with retractors, and the osteotomy was performed. Bone wax was applied to the marrow cavities, and the wound was closed in layers. (See Fig. 3 for procedural illustrations).

Fig. 3.

Modified proximal fibular osteotomy procedure. A Prone position, marking fibular head and incision. B Fibula exposure via intermuscular space. C Placement of Threading Saw Pliers, wire-saw passage, and fibular osteotomy. D Threading Saw Pliers, features a front-mounted closed-loop channel. E The wire saw passes through the closed-loop channel. F: Resected fibular segment (~2 cm)

Conventional group

The patient positioning, incision, and approach were identical. The osteotomy was performed using a free-hand technique with a wire saw or other conventional instruments without the guiding pliers.

Outcome assessment

Primary outcomes were operative time (from incision to closure), calculated blood loss (suction volume minus irrigation volume), and perioperative complication rates (including infection, swelling, nerve injury evidenced by foot drop or sensory deficit). Secondary outcomes were patient-reported pain and function, assessed using the Visual Analogue Scale (VAS), Knee Society Score (KSS), and Hospital for Special Surgery Knee Score (HSS) preoperatively and at 6 and 12 months postoperatively [9–11].

Statistical analysis

Statistical analysis was performed using SPSS version 26.0 (IBM Corp., Armonk, NY, USA). Continuous data are presented as mean ± standard deviation, if not denoted alternatively, and were compared using independent Sample t-tests. Categorical data are presented as counts (percentages) and were compared using Chi-square or Fisher’s exact tests. Intragroup comparisons of pre- and postoperative scores were performed using paired t-tests. A P-value < 0.05 was considered statistically significant.

Results

Patient demographics

Eighty patients were included. The Modified group had 21 males and 19 females with a mean age of 71.29 ± 3.11 years. The Conventional group had 22 males and 18 females with a mean age of 70.98 ± 2.98 years. There were no significant differences in baseline demographics between the two groups (Table 1), indicating well-matched cohorts for comparison.

Operative parameters

The Modified group had a significantly shorter mean operative time (25.14 ± 8.11 min vs. 55.33 ± 6.90 min, P < 0.001) and significantly less intraoperative blood loss (20.11 ± 30.29 ml vs. 101.19 ± 29.33 ml, P < 0.001) compared to the Conventional group (Table 2).

Table 2.

Comparison of operative parameters between groups (x̄ ± s)

Group	Cases	Operation time/min	Blood loss/ml
Modified	40	25.14 ± 8.11	20.11 ± 30.29
Traditional	40	55.33 ± 6.90	101.19 ± 29.33
*t*	-	6.052	7.212
P	-	< 0.001	< 0.001

Complication profiles

The overall complication rate was significantly lower in the Modified group (1/40, 2.5%) than in the Conventional group (11/40, 27.5%) (P=0.007). The complications in the Conventional group included swelling (3), muscle weakness (3), and abnormal sensation (2), while the Modified group had only one case of swelling (Table 3).

Table 3.

Comparison of postoperative complication incidence (%)

Group	Cases	Infection	Swelling	Muscle weakness	Abnormal sensation	Total incidence
Modified	40	0 (0.00)	1 (2.50)	0 (0.00)	0 (0.00)	1 (2.50)
Traditional	40	0 (0.00)	3 (7.50)	3 (7.50)	2 (5.00)	11 (27.50)
X2	-	-	-	-	-	7.314
P	-	-	-	-	-	0.007

Clinical efficacy

Preoperative VAS, KSS, and HSS scores were comparable between groups. At both the 6-month and 12-month follow-ups, both groups showed statistically significant and clinically meaningful improvements from their preoperative baselines in all functional scores (P < 0.05). There were no significant differences in any of the scores between the two groups at these time points (Table 4), indicating equivalent mid-term clinical efficacy.

Table 4.

Comparison of pain levels and joint function scores before and after surgery (x̄ ± s)

Group	Cases	VAS
		Preoperative	6 months	12 months
Modified	40	6.66 ± 1.21	3.29 ± 0.21#	1.16 ± 0.09#
Traditional	40	6.71 ± 1.19	3.31 ± 0.19#	1.15 ± 0.05#
*t*	-	0.186	0.447	0.614
P	-	0.853	0.656	0.541
Group	Cases	KSS
		Preoperative	6 months	12 months
Modified	40	72.11 ± 6.55	80.11 ± 6.55#	85.58 ± 8.19#
Traditional	40	72.18 ± 6.19	81.28 ± 5.98#	86.11 ± 7.89#
*t*	-	0.049	0.834	0.295
P	-	0.961	0.407	0.769
Group	Cases	HSS
		Preoperative	6 months	12 months
Modified	40	78.19 ± 7.11	84.19 ± 5.98#	88.98 ± 6.20#
Traditional	40	79.11 ± 6.19	84.43 ± 6.01#	89.18 ± 5.59#
*t*	-	0.617	0.179	0.152
P	-	0.539	0.858	0.88

# means P < 0.05 compared to Preoperative value within group

Imaging changes

In addition to representative cases, preoperative and 12-month postoperative weight-bearing line (WBL) ratios were assessed in all patients to evaluate changes in lower limb alignment. In the Modified group, the mean WBL ratio improved from 32.1% ± 5.8% preoperatively to 44.3% ± 6.2% postoperatively, indicating a shift toward neutral alignment. Comparable improvements were observed in the Conventional group (from 31.8% ± 6.1% to 43.9% ± 7.0%), with no significant between-group differences (P > 0.05). Representative imaging data are presented below.

Case 1

A patient underwent left proximal fibular osteotomy. Comparing pre-operative imaging with 6-month and 12-month post-operative images revealed changes in medial and lateral knee compartment heights. The distance from the fibular head to the lateral tibial plateau increased from 1.4 cm to 2.0 cm, indicating reduced fibular head support on the tibial plateau. The patient experienced pain relief and improved knee range of motion. Figure 4.

Fig. 4.

A patient, left PFO. Pre-operative, 6-month, and 12-month post-operative comparisons. A Pre-op: Fibular head to lateral tibial plateau height = 1.4 cm. B 6 months post-op: Height = 2.0 cm. C 12 months post-op: Knee joint changes and improved range of motion

Case 2

A patient underwent left fibular osteotomy. Comparing pre-operative and 3-day post-operative images showed changes in medial and lateral compartment heights, accompanied by significant pain relief. Figure 5.

Fig. 5.

A patient, left PFO. Pre-operative vs. 3-day post-operative comparison. A Pre-operative AP X-ray(left knee). B Post-operative AP X-ray(left knee)

Discussion

The pathogenesis of KOA remains incompletely understood, although genetic factors, environmental influences, age, and obesity are recognized as significant contributors [12, 13]. Current clinical management lacks disease-modifying drugs; Treatment strategies, such as pharmacological interventions (e.g., NSAIDs, corticosteroids), physical therapy, and surgical procedures, primarily focus on pain relief and delaying disease progression, albeit with variable outcomes [14, 15]. KOA primarily manifests as knee pain, deformity, and limited mobility. First-line treatment follows a conservative regimen, this is effective in approximately 50% of the cases. When conservative treatment such as physical therapy, pharmacological management (e.g., NSAIDs, intra‑articular injections), and lifestyle modifications fails operative measures are the next option. Those include joint replacement, tibial osteotomy, and fibular osteotomy [16–18]. Joint replacement is typically reserved for advanced disease with excellent long‑term survivorship but involves substantial soft tissue dissection and implant‑related considerations. Tibial osteotomy is indicated for younger, active patients with isolated medial compartment disease, yet it requires meticulous surgical technique and a prolonged protected weight‑bearing period. In this context, Proximal fibular osteotomy (PFO) has emerged as a complementary alternative, offering procedural simplicity and minimal invasiveness while achieving comparable pain relief in appropriately selected patients [19]. The procedure typically requires a 3‑4 cm incision, involves resection of a 1.5‑2 cm fibular segment, and can be performed under local anesthesia. It is cost-effective and yields favorable outcomes, often providing immediate pain relief post-operatively and enabling immediate weight-bearing [20, 21]. Zhang et al. [22, 23] proposed the “Uneven Subsidence Theory,” suggesting that PFO corrects uneven tibial plateau subsidence, thereby alleviating medial compartment KOA pain.

The complex anatomy surrounding the proximal fibula predisposes nerves and vessels to injury during PFO. Rupp RE et al. [24] dissected cadaveric limbs, finding the common peroneal nerve and anterior tibial artery traverse the middle-upper fibula, rendering them vulnerable during osteotomy. Our Threading Saw Pliers, designed to be compact and maneuverable, facilitates safe passage around the medial fibula. Its distal hollow tubular structure guides the wire saw smoothly around the fibula, minimizing nerve injury risk. This design advantage directly contributed to the superior perioperative outcomes observed in our study: the Modified group demonstrated a significantly shorter operative time (25.14 ± 8.11 min vs. 55.33 ± 6.90 min) and reduced blood loss (20.11 ± 30.29 ml vs. 101.19 ± 29.33 ml), with a markedly lower complication rate (2.5% vs. 27.5%). Furthermore, the surgical approach utilizes the intermuscular space between the peroneus longus/brevis and soleus muscles, combined with blunt dissection of the medial fibular muscles and circumferential sliding using a towel clip. This technique helps avoid damage to the peroneal artery. This modified approach significantly reduces intraoperative bleeding and postoperative hematoma risk, as evidenced by the significantly shorter operative time and reduced blood loss in the Modified group compared to the Conventional group.

PFO also effectively alters lower limb alignment loading [23, 25–27], promoting soft tissue, ligament, and muscular balance restoration [23]. Multiple studies confirm significant correction of knee varus deformity following PFO [28–30], a finding corroborated by our study, in which both groups demonstrated notable improvement in the weight-bearing line ratio postoperatively. We propose that the modified PFO described herein shifts the tibial plateau stress point laterally in KOA patients. Concurrently, posterior calf muscles exert distal traction on the fibula, reducing medial plateau load, relieving medial biological stress, halting uneven tibial plateau subsidence, and ultimately delaying osteoarthritis progression. Post-operative radiographs clearly demonstrate fibular head descent, weakened tibial plateau support, changes in medial and lateral knee compartments, and significant pain improvement. Despite these advantages, PFO is not without limitations. The procedure is primarily indicated for patients with medial compartment knee osteoarthritis and preserved lateral compartment cartilage; patients with advanced tricompartmental arthritis or significant lateral joint space narrowing may derive limited benefit. Potential complications include peroneal nerve injury due to the proximity of the common peroneal nerve to the proximal fibula, and residual or recurrent varus deformity in cases of improper patient selection. Additionally, long‑term outcome data remain less extensive compared with high tibial osteotomy or arthroplasty, warranting careful consideration in surgical decision‑making.

Limitations

This study has several limitations that must be acknowledged. Firstly, its retrospective design is subject to inherent biases, particularly selection bias due to non-randomized patient allocation based on chronological order. Although this sequential grouping reflects the pragmatic introduction of the new tool, it may introduce confounding factors such as the surgeon’s learning curve over time, which could influence operative parameters. Additionally, information bias may arise from reliance on existing medical records. Future prospective, randomized controlled trials with larger cohorts and extended follow-up are warranted to validate these findings and provide higher-level evidence. Secondly, the sample size, while sufficient to detect significant differences in the primary outcomes, remains relatively small. Thirdly, the follow-up duration of 12 months, while adequate for assessing perioperative safety and mid-term functional outcomes, is insufficient to evaluate the long-term durability of the results or the potential for late sequelae. Future prospective, randomized controlled trials with larger cohorts and extended follow-up periods are warranted to validate these findings and assess long-term efficacy.

Conclusion

In conclusion, this study demonstrates that the modified proximal fibular osteotomy using the Threading Saw Pliers is a safe, efficient, and effective treatment for MKOA. It offers substantial perioperative advantages over traditional surgery, including markedly reduced operating time, decreased intraoperative blood loss, and a significantly lower postoperative complication rate, Additionally it provides equivalent and excellent mid-term pain relief and functional improvement. The Threading Saw Plier is a beneficial technical advancement in the execution of PFO.

Authors' contributions

Zhenguo Cao: Conceptualization, Methodology. Junwei Zhang and Ziyang Li: Writing–Original Draft, Validation, Writing–Review & Editing. Xingjuan Zhou: Data Curation, Formal Analysis, Investigation. Gen Li and Xuebin Tang: Resources, Software, Visualization. Hua Li and Yunqing Wang: Supervision, Project administration. All authors read and approved the final manuscript.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This single-center, retrospective, comparative cohort study was approved by the Institutional Review Board of the Second Affiliated Hospital of Xuzhou Medical University (Ethics No.:【2025】060101). This study adhered to the principles of the Declaration of Helsinki and was conducted in accordance with national ethical guidelines. The requirement for informed consent was waived by the IRB due to the retrospective nature of the study and the use of de-identified patient data.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.