Influence of the BMI (<30 kg/m 2 vs. ≥30 kg/m 2 ) on the Surgical Outcome of Osteochondral Lesions of the Talus: Prospective Data from the German Cartilage Registry (KnorpelRegister DGOU)

Abstract

Objective

Aim of this study was to evaluate the 24 months follow-up data of the German Cartilage Registry (KnorpelRegister DGOU, GCR) regarding the influence of body mass index (BMI) on clinical outcomes after surgical osteochondral lesions of the talus (OCT) treatment.

Design

A total of 303 patients met the inclusion criteria. Pre- and post-operative Foot and Ankle Outcome Score (FAOS) total scores, subscores, and ΔFAOS were analyzed for most frequent surgical techniques (bone marrow stimulation [BMS], matrix-augmented BMS, matrix-augmented BMS with additional bone grafting) in normal weight group (NW, BMI <30 kg/m², n = 228) and obese weight group (OW, BMI ≥30 kg/m², n = 75).

Results

BMI was significantly different in NW and OW (24.6 ± 2.97 [16.9-29.9] kg/m² vs. 33.7 ± 4.0 [30.0-51.3] kg/m², P < 0.001). Significant improvement from pre- to post-operative FAOS score and subscales was reached in both groups (NW: 64.2 ± 17.5 vs. 77.7 ± 17.8; OW: 52.3 ± 15.5 vs. 73.5 ± 20.2; P < 0.001) with higher pre- and post-operative scores in NW. No significant difference in ΔFAOS score was detected. Treatment technique did not influence the clinical outcome. OW showed an extended use of bone grafting due to greater defect depth. Age was significantly higher in OW compared to NW (35.7 ± 13.2 [18.0-69.0] years vs. 40.7 ± 13.1 [18.0-77.0] years, P = 0.005).

Conclusions

Patients benefit from surgical cartilage therapy regardless of their BMI. OW showed significantly lower pre- and post-operative FAOS scores. In OW, additional bone grafting was required more frequently due to significantly deeper defects.

Keywords

OCT talus BMI obesity cartilage regeneration

Introduction

Osteochondral lesions of the talus (OCTs) are a common cause of ankle pain.¹ Both acute ankle sprains and chronic misload of the ankle joint aggravated by high weight loads can lead to symptomatic OCTs.^2,3 Since the incidence of overweight and obesity is rapidly increasing over the last decade^4,5 and a higher body mass index (BMI) is associated with a higher prevalence of ankle sprains and OCTs^6,7 the influence of an increased BMI on the outcome of surgical treated OCTs has gained clinical importance. According to the World Health Organization (WHO), obesity is defined as BMI ≥30 kg/m² (Sørensen et al.⁸), affecting 19% of the German population.⁴ In the United States, more than one third of the population is considered to be obese and in 2030 an estimated rate of 50% will suffer from obesity.^9,10 Beside cardiovascular and metabolic consequences, changes in joint loading and mechanical characteristics of joint cartilage are also described.^11-13 Overall, rates of foot and ankle pain are increased in obese patients.¹⁴ Therefore, obesity is a relevant clinical factor having to be considered in the treatment of OCTs. Klammer et al.¹⁵ did not find a correlation of BMI and the outcome of conservatively treated OCTs. The influence of BMI on surgically treated OCTs has also been discussed in several prior studies with contradicting results. While some studies revealed worse outcomes after surgical therapy of OCTs with increasing BMI,^16,17 other studies did not find any influence.^18,19 There is also evidence of higher postoperative satisfaction in patients with higher BMI.²⁰

Current literature is limited by strict inclusion criteria of Randomized Controlled Trials (RCTs) mostly excluding excessive factors like high BMIs. So, RCTs often do not represent the whole patient cohort suffering from OCTs and being treated in real life.^21,22 Körner et al.²³ already analyzed the correlation of BMI and preoperative joint function and clinical complaints in patients with OCTs using registry data from the German Cartilage Registry (GCR). The authors did not find any correlation preoperatively, but postoperative outcomes were not examined. The purpose of this study was to analyze the registry data of the German Cartilage Registry (KnorpelRegister DGOU) for real-time treatment patterns of OCTs and their outcome in patients with BMI <30 kg/m² and patients with BMI ≥30 kg/m².

Material and Methods

Registry Data

The used data are based on registry data obtained from the German Cartilage Registry (GCR, KnorpelRegister DGOU) from its implementation in 2015 to June 2021.

At the time of data collection in June 2021, the ankle database included 940 patients. Registry data collection is conducted by a web-based Remote Data Entry System. Patients undergoing surgical treatments of ankle OCT are enclosed after written consent. Prospectively, patient data, lesion characteristics, symptoms, and outcomes are recorded at specific time points (6, 12, 24, 36, and 60 months after surgery). Intraoperative data, i.e. lesion size and performed treatment technique, are entered by the responsible surgeon.

Study Design

For this prospective study, all patients with an isolated osteochondral lesion of the talus with a completed FAOS subscale pain score 24 months postoperatively as primary outcome parameter and a completely described defect size recorded in GCR until June 2021 have been included. Afterwards, patients were divided into a cohort with BMI <30 kg/m² (normal weight group, NW) and BMI ≥ 30 kg/m² (obese weight group, OW).

Outcome Measures

The FAOS score, validated in German language, was used. The subscale pain was used as primary outcome parameter pre- and 2-years post-operative. The other 4 subscales Symptoms (S), Activity of Daily Living (ADL), Sport and Recreation Ability (Sports/Rec), and Foot and Ankle-related Quality of Life (QoL) have been additionally analyzed. A further analysis of possible confounding factors on FAOS total score and subscores was performed, including most frequent surgical techniques (i.e. BMS, matrix-augmented bone marrow stimulation [mBMS], and mBMS with additional bone grafting), defect size area and defect volume, patient age and duration of symptoms. In addition, a subgroup analysis in revision surgery was conducted.

Statistical Analysis

Statistical analysis was performed via SPSS software (version 28.0.0; SPSS Inc., Chicago, IL, USA). Outcome parameters were evaluated concerning normal distribution. Afterwards, standard deviations (SDs) were calculated for continuous variables. To detect differences of outcome scores between BMI groups and treatment modalities a univariate t test (analysis of variance [ANOVA]) with a post hoc Duncan test was applied. Also patient and lesion characteristics as possible confounding parameters (i.e. age, symptom duration, lesion size area, lesion size volume) have been evaluated for both study groups and tested for significant differences as described before. Subgroup analysis in patients with prior surgery on OCT was performed in the same way as described before for the whole collective of patients.

The level of significance was set at 95%. Tested comparisons with a P-level < 0.05 were considered to be significantly different.

Ethical Agreement

KnorpelRegister DGOU has been implemented with accordance of nationwide local ethic committees and in consent with the Declaration of Helsinki. All participants provided written consent prior to inclusion in the registry.

Results

Patient Characteristics

Until June 2021, the ankle module of the GCR included 940 patients. These patients were screened for single OCT (n = 867), complete information on defect size (n = 813), and complete FAOS subscore pain after 24 month (n = 303).

Overall, a total of 303 patients aged between 18 and 77 years met the inclusion criteria and were divided into 2 groups according to their BMI. A total of 228 patients had a BMI <30 kg/m². The mean BMI was 24.6 ± 3.0 (16.9-29.9) kg/m². In total, 110 (48.2%) of them were female and 118 patients were male (51.2%). The mean symptom duration was 30.2 ± 43.9 (0.0-336.0) months.

Seventy-five patients had a BMI ≥30 kg/m². The mean BMI was 33.7 ± 4.0 (30.0-51.3) kg/m². In this group, 44 (58.6%) were female and 31 (41.3%) were male. Mean symptom duration was 30.8 ± 46.4 (2.0 ± 288.0) months.

The mean age was significantly lower in NW (35.7 ± 13.2 [18.0-69.0] years vs. 40.7 ± 13.1 [18.0-77.0] years, P = 0.005). Other demographic data were not significantly different between both cohorts ( Table 1 ).

Table 1.

Patient and Lesion Characteristics.

Characteristics	Total	BMI <30	BMI ≥30	P
Age at time of surgery	37.0 ± 13.4 (18.0-77.0)	35.7 ± 13.2 (18.0-69.0)	40.7 ± 13.1 (18.0-77.0)	0.005
Sex
Male	149 (49.2)	118 (51.8)	31 (41.3)
Female	154 (50.8)	110 (48.2)	44 (58.7)
BMI (kg/m²)	26.9 ± 5.1 (16.9-51.3)	24.6 ± 3.0 (16.9-29.9)	33.7 ± 4.0 (30.0-51.3)	<0.001
Duration of Symptoms [months]	30.3 ± 44.5 (0.0-336.0)	30.2 ± 43.9 (0.00-336.00)	30.8 ± 46.4 (2.0-288.0)	0.913
Previous surgery on the respective ankle
None	191 (63.0)	145 (63.6)	46 (61.3)
1	82 (27.1)	62 (27.2)	20 (26.7)
≥2	30 (9.9)	21 (9.2)	9 (12.0)
Previous surgery on OLT
No	225 (74.3)	172 (76.1)	53 (70.7)
Yes	76 (25.1)	54 (23.9)	22 (29.3)
Lesion size (Length × width [mm²])	133.8 ± 96.2 (4.0-600.0)	131.4 ± 93.8 (4.0-580.0)	141.0 ± 103.6 (6.0-600.0)	0.454
Lesion volume (Length × width × height [mm³])	852.7 ± 1,149.0 (4.0-10,450.0)	786.5 ± 1,062.8 (4.0-10,450.0)	1,054.0 ± 1,366.9 (6.0-7,168.0)	0.08
Lesion volume (ellipsoid [mm³])	446.5 ± 601.6 (2.1-5,471.6)	411.8 ± 556.5 (2.1-5,471.6)	551.9 ± 715.7 (3.1-3,753.2)	0.08
Defect depth (mm)	5.4 ± 3.9 (1.0-25.0)	5.1 ± 3.7 (1.0 – 25.0)	6.2 ± 4.3 (1.0-20.0)	0.041

Demographic data and lesion characteristics are depicted as mean ± standard deviation (range or %).

BMI = body mass index.

Pre- and Post-operative FAOS Scores

Significant improvement from pre- to post-operative scores was reached in the FAOS total score and all FAOS subscales for both BMI groups (P < 0.001) ( Fig. 1 ). Preoperative scores were significantly higher in NW including the total score and subscales Activity, Symptoms, and Sports/Rec. The postoperative scores also tended to be higher in this group, reaching significance in the subscales Symptoms and Sports/Rec. The FAOS subscale QoL showed no significant differences between both cohorts. No significant differences in the ΔFAOS scores were detected for total score and subscales except for the subscale pain with a higher absolute increase in OW (Fig. 1; Table 2).

Figure 1.

Results of FAOS total score and subscales in relation to BMI classification with dark gray representing BMI <30 kg/m² and light gray representing BMI ≥ 30 kg/m². There is a significant increase from pre- to post-operative scores in every scale for both groups (P < 0.001). Patient group with BMI <30 kg/m² showed higher scores pre- and post-operatively partly reaching significance. Delta did not reveal differences between both groups except for subscale pain with significant higher absolute increase in higher BMI group. * P < 0.05; ** P < 0.01; *** P < 0.001.

Table 2.

Analysis of FAOS Subscales and Total Score Between Both BMI Groups.

FAOS score	BMI <30	BMI ≥30	P
Activity preop.	77.0 ± 21.2 (0.0 to 100.0)	65.6 ± 18.0 (22.1 to 100.0)	<0.001
Activity postop.	87.4 ± 15.3 (20.6 to 100.0)	83.6 ± 18.5 (13.2 to 100.0)	0.105
Delta activity	12.5 ± 21.1 (−23.5 to 94.1)	18.6 ± 19.5 (−17.7 to 70.6)	0.072
Pain preop.	65.0 ± 19.2 (11.1 to 100.0)	50.4 ± 20.1 (0.0 to 83.3)	<0.001
Pain postop.	80.1 ± 18.9 (11.1 to 100.0)	74.7 ± 21.6 (22.2 to 100.0)	0.039
Delta pain	16.9 ± 20.6 (−36.1 to 72.2)	23.6 ± 25.3 (−41.7 to 91.7)	0.037
QoL preop.	31.3 ± 17.8 (0.0 to 93.8)	27.0 ± 17.0 (0.0 to 68.8)	0.090
QoL postop	50.7 ± 25.6 (0.0 to 100.0)	46.1 ± 25.9 (0.0 to 100.0)	0.184
Delta QoL	20.2 ± 25.2 (−37.5 to 81.3)	18.4 ± 26.0 (−25.0 to 87.5)	0.608
Symptoms preop.	63.6 ± 21.1 (14.3 to 100.0)	50.7 ± 19.9 (14.3 to 96.4)	<0.001
Symptoms postop.	73.0 ± 22.2 (10.7 to 100.0)	66.3 ± 22.9 (10.7 to 100.0)	0.027
Delta symptoms	10.4 ± 24.3 (−57 to 1 to 82.1)	15.7 ± 21.3 (−28.6 to 60 to 7)	0.123
Sports preop.	40.8 ± 26.2 (0.0 to 100.0)	30.7 ± 21.2 (0.0 to 100.0)	0.007
Sports postop.	65.1 ± 27.6 (0.0 to 100.0)	57.0 ± 30.7 (5.0 to 100.0)	0.042
Delta sports	25.9 ± 30.6 (−65.0 to 100.0)	25.4 ± 31.6 (−50.0 to 100.0)	0.910
Total preop.	64.2 ± 17.6 (11.3 to 99.4)	52.3 ± 15.5 (16.7 to 85.7)	<0.001
Total postop.	77.7 ± 17.8 (12.5 to 100.0)	73.5 ± 20.2 (17.3 to 100.0)	0.127
Delta total	15.2 ± 18.8 (−17.9 to 68.5)	20.5 ± 19.9 (−19.1 to 64.9)	0.128

FAOS scores are depicted as mean ± standard deviation (min-max).

BMI = body mass index.

Analysis of Treatment Techniques

The most frequent therapy techniques were BMS (26.4%), mBMS (25.1%), and mBMS with additional bone grafting (mBMS + SP, 33.3%).

In NW, all 3 techniques were represented equally ( Fig. 2 ). No statistically relevant differences in FAOS total score has been observed between the 3 surgical techniques ( Fig. 3A ). The OW showed an excessive representation of additional bone grafting ( Fig. 2 ). Analysis of outcomes between these surgical techniques showed no statistically relevant differences within OW for both FAOS subscales and FAOS total score ( Fig. 3A ).

Figure 2.

Percentage distribution of most frequent therapy techniques in patient cohort with BMI <30 and patient cohort with BMI >30. In patients with BMI <30 BMS. mBMS and mBMS + SP are represented equally. In patients with BMI ≥30 additional bone grafting has been used in most cases. BMS = bone marrow stimulation; mBMS = matrix-augmented bone marrow stimulation; mBMS + SP = matrix-augmented bone marrow stimulation with additional spongiosaplasty.

Figure 3.

Analysis of FAOS total score dependent on surgical technique and BMI. (A) There were no differences in FAOS total scores between different techniques for both BMI groups. (B) Among patients being treated with a specific technique, i.e. BMS, mBMS, or mBMS + SP, there were no differences in FAOS total scores in relation to the underlying BMI. BMS = bone marrow stimulation; mBMS = matrix-augmented bone marrow stimulation; mBMS + SP = matrix-augmented bone marrow stimulation with additional spongiosaplasty. * P < 0.05; ** P < 0.01; *** P < 0.001.

Subgroup analysis for BMS, mBMS, and mBMS + SP showed similar results to the overall analysis with higher pre- and post-operative FAOS scores for NW and significant increases from pre- to post-operative scores for both BMI groups (P < 0.001). The ΔFAOS score was not different between both groups ( Fig. 3B ; Tables 3 –5).

Table 3.

Analysis of FAOS Total Between Both BMI Groups Treated with BMS.

FAOS score	BMI <30	BMI ≥30	P
Activity preop.	79.3 ± 22.2 (0.0 to 100.0)	64.7 ± 20.8 (33.8 to 100.0)	0.053
Activity postop.	87.7 ± 14.3 (47.1 to 100.0)	85.3 ± 12.1 (63.2 to 100.0)	0.563
Delta activity	10.0 ± 22.3 (−16.2 to 94.1)	19.3 ± 18.6 (−1.7 to 50.0)	0.234
Pain preop.	63.9 ± 18.9 (25.0 to 100.0)	50.0 ± 22.9 (25.0 to 83.3)	0.039
Pain postop.	79.0 ± 18.6 (36.1 to 100.0)	75.4 ± 16.7 (47.2 to 100.0)	0.471
Delta pain	17.0 ± 23.2 (−36.1 to 72.2)	23.7 ± 24.5 (−19.4 to 58.3)	0.389
QoL preop.	31.9 ± 17.1 (0.0 to 93.8)	25.0 ± 16.3 (0.0 to 50.0)	0.229
QoL postop	49.2 ± 25.7 (0.0 to 100.0)	43.0 ± 21.5 (12.5 to 81.3)	0.373
Delta QoL	18.6 ± 26.5 (−25.0 to 81.3)	15.3 ± 18.8 (0.0 to 62.5)	0.698
Symptoms preop.	64.6 ± 21.0 (21.4 to 100.0)	43.5 ± 17.3 (17.9 to 67.9)	0.003
Symptoms postop.	73.6 ± 22.6 (28.6 to 100.0)	59.2 ± 18.5 (28.6 to 89.3)	0.022
Delta symptoms	9.5 ± 27.1 (−46.3 to 78.6)	13.6 ± 22.4 (−21.4 to 57.1)	0.639
Sports preop.	43.3 ± 25.5 (0.0 to 100.0)	32.7 ± 21.5 (0.0 to 70.0)	0.207
Sports postop.	65.7 ± 29.9 (0.0 to 100.0)	54.0 ± 25.7 (15.0 to 90.0)	0.170
Delta sports	23.4 ± 34.8 (−30.0 to 100.0)	23.0 ± 21.0 (−5.0 to 100.0)	0.970
Total preop.	64.8 ± 18.9 (11.3 to 99.4)	50.4 ± 17.3 (25.0 to 81.0)	0.029
Total postop.	72.6 ± 14.7 (41.7 to 100.0)	72.6 ± 14.7 (52.4 to 92.9)	0.370
Delta total	14.8 ± 22.2 (−16.7 to 68.5)	21.6 ± 17.1 (2.4 to 53.0)	0.402

FAOS scores are depicted as mean ± standard deviation (min-max).

BMI = body mass index.

Table 4.

Analysis of FAOS Total Between Both BMI Groups Treated With mBMS.

FAOS score	BMI <30	BMI ≥30	P
Activity preop.	71.5 ± 24.2 (4.4 to 100.0)	59.4 ± 18.5 (22.1 to 79.4)	0.144
Activity postop.	86.4 ± 16.3 (20.6 to 100.0)	80.0 ± 27.8 (13.2 to 100.0)	0.285
Delta activity	17.2 ± 24.5 (−19.1 to 80.9)	19.5 ± 16.1 (−11.8 to 41.2)	0.802
Pain preop.	62.8 ± 19.5 (19.4 to 100.0)	44.4 ± 24.2 (2.8 to 77.8)	0.009
Pain postop.	79.8 ± 18.6 (11.1 to 100.0)	69.4 ± 28.6 (22.2 to 100.0)	0.097
Delta pain	18.5 ± 19.2 (−13.9 to 66.7)	19.7 ± 23.1 (−16.7 to 55.6)	0.858
QoL preop.	28.2 ± 18.2 (0.0 to 68.8)	22.4 ± 18.7 (0.0 to 62.5)	0.325
QoL postop	49.9 ± 26.5 (0.0 to 100.0)	47.6 ± 37.4 (0.0 to 100.0)	0.793
Delta QoL	22.1 ± 23.6 (−18.8 to 75.0)	20.5 ± 35.3 (−18.8 to 75.0)	0.847
Symptoms preop.	57.6 ± 20.7 (14.3 to 92.9)	48.5 ± 23.3 (14.3 to 82.1)	0.184
Symptoms postop.	69.4 ± 21.6 (10.7 to 100.0)	63.8 ± 28.5 (10.7 to 100.0)	0.414
Delta symptoms	13.6 ± 20.2 (−28.6 to 67.9)	12.8 ± 19.3 (−21.4 to 39.3)	0.906
Sports preop.	32.1 ± 25.3 (0.0 to 100.0)	25.0 ± 20.3 (0.0 to 55.0)	0.428
Sports postop.	61.9 ± 27.7 (0.0 to 100.0)	50.8 ± 39.0 (5.0 to 100.0)	0.230
Delta sports	32.3 ± 27.0 (−25.0 to 100.0)	16.3 ± 43.3 (−50.0 to 100.0)	0.165
Total preop.	60.1 ± 17.9 (24.2 to 92.3)	48.0 ± 17.6 (16.7 to 66.1)	0.073
Total postop.	75.2 ± 18.2 (12.5 to 99.4)	68.5 ± 30.8 (17.3 to 100.0)	0.341
Delta total	18.9 ± 19.0 (−14.3 to 61.3)	14.2 ± 23.6 (−19.1 to 45.8)	0.589

FAOS scores are depicted as mean ± standard deviation (min-max).

BMI = body mass index.

Table 5.

Analysis of FAOS Total Between Both BMI Groups Treated With mBMS + SP.

FAOS score	BMI <30	BMI ≥30	P
Activity preop.	78.9 ± 18.6 (39.7 to 100.0)	69.1 ± 14.6 (29.4 to 94.1)	0.027
Activity postop.	87.0 ± 16.9 (30.0 to 100.0)	85.6 ± 15.8 (42.7 to 100.0)	0.729
Delta activity	9.4 ± 16.6 (−25.5 to 58.8)	15.8 ± 15.7 (−17.7 to 52.9)	0.142
Pain preop.	67.1 ± 18.7 (25.0 to 100.0)	55.8 ± 13.8 (22.2 to 80.6)	0.004
Pain postop.	80.0 ± 20.7 (27.8 to 100.0)	77.0 ± 18.9 (33.3 to 100.0)	0.477
Delta pain	15.3 ± 19.1 (−27.8 to 69.4)	22.0 ± 20.4 (−22.2 to 61.1)	0.124
QoL preop.	32.5 ± 17.8 (0.0 to 81.25)	27.0 ± 16.4 (0.0 to 62.5)	0.142
QoL postop	51.1 ± 24.9 (0.0 to 100.0)	46.7 ± 25.5 (6.25 to 100.0)	0.412
Delta QoL	21.3 ± 25.8 (−37.5 to 81.3)	20.4 ± 26.9 (−25.0 to 87.5)	0.878
Symptoms preop.	69.6 ± 20.6 (14.3 to 100.0)	52.1 ± 19.6 (14.3 to 96.4)	<0.001
Symptoms postop.	75.6 ± 21.2 (10.7 to 100.0)	70.9 ± 21.8 (25.0 to 100.0)	0.313
Delta symptoms	7.9 ± 23.9 (−57.1 to 53.6)	19.1 ± 19.0 (−25.0 to 57.1)	0.023
Sports preop.	46.2 ± 26.7 (0.0 to 100.0)	31.2 ± 21.1 (0.0 to 100.0)	0.009
Sports postop.	66.4 ± 27.1 (0.0 to 100.0)	60.5 ± 27.7 (10.0 to 100.0)	0.330
Delta sports	21.6 ± 27.3 (−65.0 to 90.0)	28.2 ± 26.4 (−20.0 to 85.0)	0.291
Total preop.	66.8 ± 17.1 (30.4 to 95.8)	56.9 ± 12.5 (23.2 to 81.0)	0.013
Total postop.	79.4 ± 18.3 (32.7 to 100.0)	76.5 ± 16.7 (39.3 to 100.0)	0.508
Delta total	12.8 ± 17.3 (−17.9 to 64.3)	18.2 ± 15.4 (−11.9 to 45.8)	0.261

FAOS scores are depicted as mean ± standard deviation (min-max).

BMI = body mass index.

Lesion Characteristics

There was a tendency of higher defect size volumes in OW (411.8 ± 556.5 [2.1-5,471.6] mm³ vs. 551.9 ± 715.7 [3.1-3,753.2] mm³; P = 0.08) and a significantly greater mean defect depth in OW (5.1 ± 3.73 [1.0-25.0] mm vs. 6.2 ± 4.3 [1.0-20.0] mm, P = 0.041) ( Table 1 ).

Subgroup Analysis of Revision Surgery

Subgroup analysis of patients with revision surgery revealed similar findings for both BMI cohorts with significant increase from pre- to post-operative FAOS scores in both study groups. Also in revision surgery, OW documented severe complaint in FAOS subscales pain and symptoms (Supplemental Table S1).

Discussion

The current study analyzed the influence of BMI (< 30kg/m² vs. ≥ 30 kg/m²) on the surgical outcome of OCTs. The most important finding was that all patients suffering from single OCT benefit from surgical therapy regardless from their underlying BMI. Significant improvement from pre- to post-operative FAOS score and subscales was reached in both groups, but significantly higher pre- and post-operative scores were detected in NW. No significant difference in ΔFAOS score was identified between both groups reflecting similar improvements for both groups. Due to greater defect depths, additional bone grafting was performed more frequently in patients with BMI ≥30 kg/m².

With increasing prevalence of obesity, the relevance of the influence of BMI on the outcome of surgically treated OCTs is growing. Since both the incidence of ankle sprains and also joint load is increasing with higher BMI an effect on the prevalence of OCTs and resulting clinical symptoms has been discussed in the literature.^7,24,25 Indeed, a higher rate of OCTs has been found in ankle arthroscopies performed in cases of ankle impingement syndrome.⁶ Furthermore, a positive correlation of BMI and defect size has been described,²⁶ and in overweight patients with BMI ≥25 kg/m², a pronounced bone edema in magnetic resonance imaging (MRI) was shown.²⁷ Nevertheless, an influence on preoperative clinical symptoms and joint function was not found by Körner et al.²³ Interestingly, in our study, significantly lower FAOS total score and FAOS subscores in patients with BMI ≥30 kg/m² were found. This is in accordance with a prospective study by Brulc et al.²⁸ showing a negative correlation of higher BMI and preoperative joint status recorded in patient-reported outcome measures (PROMs). Worse clinical symptoms and complaints preoperatively could be a result of a pronounced bone edema as described before. In the present study, there were significantly deeper lesions in OW. However, lesion size volume only tended to be higher but did not reach significant differences measured neither ellipsoidal nor cuboidal.

Similarly, postoperative scores were significantly lower in OW. As demonstrated in several studies before, the postoperative outcome significantly correlates with the preoperative status.^29,30

Interestingly, both preoperative and postoperative FAOS subscale QoL score were not significantly different between both BMI groups. This is in accordance with the findings by Koh et al.,²⁰ showing a higher satisfaction in patients with BMI ≥25 kg/m². The authors attributed the higher satisfaction rate to a lower demand for activity in obese patients. Nevertheless, joint function score did not correlate with BMI in their study indicating a non-inferiority in functional and clinical aspects.

Primarily, our study aimed to analyze the influence of BMI on the surgical outcome of OCT. In this regard, a significant increase from pre- to post-operative FAOS total score und FAOS subscales has been found in both BMI groups. Thus, patients with OCT benefit from operative treatment independently from their underlying BMI exceeding the minimal important change (MIC) for FAOS score.^31,32 ΔFAOS was not significantly different between both groups, except for the subscale pain with significant higher improvement in OW. This is important since many surgeons avoid surgical treatment in obese patients due to reservations about worse outcomes. Absolute postoperative status is known to depend rather on preoperative status.^29,30 Perioperative complications due to compromised visualization, longer operating times. and an increased risk for surgical side infections in case of obesity³³ have not been recorded in this study, but even if there would have been more complications, the mid-term outcome after 24 months is not diminished. A follow-up of 2 years has been chosen due to the regeneration time of osteochondral lesions of 1 year and a described pronounced deterioration after 2 years, particularly after treatment with BMS with in up to 52% after a follow-up of 3 years.^34-36 However, promising results for long-term survival have been published recently.³⁷ Also for mBMS mid-term results after 2 years have shown promising results with the greatest improvement within the first 2 years and no further differences after 5 years.^29,38,39 No differences in postoperative outcome in 24 months follow-up regarding FAOS score after BMS, mBMS, and mBMS with additional bone grafting in both cohorts could be detected in the current study. The comparison of both groups within 1 treatment technique did not reveal significant differences in absolute clinical improvement meaning that there is no superior surgical technique for specific BMI groups. Similarly to the whole collective of patients, absolute pre- and post-operative scores tended to be higher in NW reaching significance in some subscales. Interestingly, there was an excessive use of additional bone grafting in OW accounting for 52.4% of procedures being documented. In NW, bone grafting was performed in 35.0%. According to current recommendations for cartilage therapy, bone grafting for reconstruction of subchondral bone is suggested for lesions exceeding 3 to 5 mm in depth.^40-42 In this study, significantly greater defect depths in OW could be assessed. Symptom duration was not significantly different between both groups, so that an OCT progress over a longer time period can be excluded.

Beside lesion characteristics, also patient characteristics could be influencing factors for surgical outcome after OCTs. Patient age was significantly higher in OW. Patient age has been discussed in the literature before with contradicting results. Worse results due to diminished regenerative capacity in older patients have not been demonstrated until now. An influence of patient age cannot be completely excluded. Nevertheless, since patients were older in OW, it can be noted that obese patients reached equivalent postoperative outcomes after OCT surgical therapy despite a higher patient age. Matched pair analyses are needed.

Overweight has been shown to be a risk factor for revision surgery after BMS of OCT.⁴³ The present study found similar results to primary surgery in revision surgery detecting no significant influence of BMI on surgical outcome in revision surgery at 24 months follow-up. Indeed, in contrast to primary surgery, differences in absolute pre- and post-operative scores between both BMI groups seem to be diminished. ΔFAOS was similar between both groups.

There are some limitations that need to be addressed. Even if registry data have benefits regarding real-life treatment patterns compared to highly structured RCTs, they are accompanied by disadvantages arising from the observational character and a big data set obtained from a variety of clinics. This results in a high heterogeneity regarding details in technical procedures, surgeon expertise, and after-treatment protocols. Lesion size characteristics highly depend on the data collection technique. Since MRI is known to overestimate defect size due to the surrounding bone edema,⁴⁴ weight bearing computed tomography (WBCT) with distance mapping has shown a good precision in determining defect volumes.⁴⁵ Nevertheless, a homogenous preoperative lesion characterization via CT imaging cannot be assumed due to insufficient availability. Ordinarily, definite lesion size area and lesion depth recorded intraoperatively should be documented in the registry building up the data all registry studies rely on.

Furthermore, the obese cohort size was smaller than the normal weight cohort size according to the population distribution of OCTs.⁴⁶ Moreover, clinical outcomes have been analyzed only at 24 months follow-up. Regarding the influence of BMI on surgical outcomes, it would be very interesting to consider the early regeneration time and the long-term development to detect a possible premature deterioration of regenerated cartilage in obese patients due to chronic inflammation and higher joint load.

Conclusions

Both obese and normal weight patients significantly benefit from surgical cartilage therapy. There was no influence of obese BMI on clinical outcome of surgically treated OCTs at 24 months follow-up independently from the performed surgical technique, i.e. BMS, mBMS, or mBMS with additional bone grafting. In patients with BMI ≥30 kg/m², additional bone grafting was required more frequently due to significantly deeper defects. Obese patients showed significantly lower pre- and post-operative FAOS scores, but ΔFAOS was not significantly different.

Supplemental Material

sj-docx-1-car-10.1177_19476035241301294 – Supplemental material for Influence of the BMI (<30 kg/m² vs. ≥30 kg/m²) on the Surgical Outcome of Osteochondral Lesions of the Talus: Prospective Data from the German Cartilage Registry (KnorpelRegister DGOU)

Supplemental material, sj-docx-1-car-10.1177_19476035241301294 for Influence of the BMI (<30 kg/m² vs. ≥30 kg/m²) on the Surgical Outcome of Osteochondral Lesions of the Talus: Prospective Data from the German Cartilage Registry (KnorpelRegister DGOU) by Alena Richter, Anna Altemeier, Christoph Becher, Marco Güllmann, Christian Plaass and Sarah Ettinger in CARTILAGE

Footnotes

Acknowledgments and Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethical Approval

KnorpelRegister DGOU has been implemented with accordance of nationwide local ethic committees and in consent with the Declaration of Helsinki.

Consent to Participate

All participants provided written consent prior to inclusion in the registry.

Consent for Publication

Not applicable.

ORCID iDs

Alena Richter

Christian Plaass

Sarah Ettinger

Data Availability

All data generated or analyzed during this study are included in this published article and its supplementary information files.

Supplementary material for this article is available on the Cartilage website at .

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Supplementary Material

Please find the following supplemental material available below.

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Influence of the BMI (<30 kg/m 2 vs. ≥30 kg/m 2 ) on the Surgical Outcome of Osteochondral Lesions of the Talus: Prospective Data from the German Cartilage Registry (KnorpelRegister DGOU)

Abstract

Objective

Design

Results

Conclusions

Keywords

Introduction

Material and Methods

Registry Data

Study Design

Outcome Measures

Statistical Analysis

Ethical Agreement

Results

Patient Characteristics

Pre- and Post-operative FAOS Scores

Analysis of Treatment Techniques

Lesion Characteristics

Subgroup Analysis of Revision Surgery

Discussion

Conclusions

Supplemental Material

sj-docx-1-car-10.1177_19476035241301294 – Supplemental material for Influence of the BMI (<30 kg/m2 vs. ≥30 kg/m2) on the Surgical Outcome of Osteochondral Lesions of the Talus: Prospective Data from the German Cartilage Registry (KnorpelRegister DGOU)

Footnotes

Acknowledgments and Funding

Declaration of Conflicting Interests

Ethical Approval

Consent to Participate

Consent for Publication

ORCID iDs

Data Availability

References

Supplementary Material

sj-docx-1-car-10.1177_19476035241301294 – Supplemental material for Influence of the BMI (<30 kg/m² vs. ≥30 kg/m²) on the Surgical Outcome of Osteochondral Lesions of the Talus: Prospective Data from the German Cartilage Registry (KnorpelRegister DGOU)