Treatment Reality of Tension Band Wiring and Locked Plate Fixation of the Olecranon - Analysis of Complications, Risk Profiles and Trends
Conditions: Olecranon Fracture
Sponsor: University Hospital Muenster

 
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Treatment reality of tension band wiring and locked 
plate fixation of the olecranon – analysis of 
complications, risk profiles and trends 
Short Study Protocol 
Version 1.1 
Date: August 30, 2024 
 
Coordinating Investigators: 
Prof. Dr. med. J. Christoph Katthagen 
University Hospital Münster 
Klinik für Unfall-, Hand- und Wiederherstellungschirurgie 
Albert-Schweitzer-Campus 1, Building W1 
D-48149 Münster 
Priv.-Doz. Dr. med. Josef Stolberg-Stolberg  
University Hospital Münster 
Klinik für Unfall-, Hand- und Wiederherstellungschirurgie 
Albert-Schweitzer-Campus 1, Building W1 
D-48149 Münster 
Dr. rer. nat. Jeanette Köppe, M. Sc. 
(Biostatistician) 
University of Münster 
Institute of Biostatistics and Clinical Research 
Schmeddingstraße 56 
D-48149 Münster 
 
 

 
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Signatures 
 
Coordinating Investigator 
 
Prof. Dr. med. J. Christoph Katthagen 
  
________________________________________
Place, date 
 
 
________________________________________ 
Signature 
 
Priv.-Doz. Dr. med. Josef Stolberg-Stolberg  
 
 
________________________________________
Place, date 
 
 
________________________________________ 
Signature 
 
Dr. rer. nat. Jeanette Köppe, M. Sc.   
________________________________________ 
(Biostatistician)  
 
 
 
Place, date 
________________________________________ 
Signature 
 
 
 
 
 
 

 
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Table of Contents 
 ................................................................................................................................................................. 1 
1. 
Background of the Study ................................................................................................................. 4 
2. 
Population ....................................................................................................................................... 4 
2.1. 
Treatment Groups ................................................................................................................... 4 
2.2. 
Inclusion and Exclusion Criteria ............................................................................................... 5 
3. 
Endpoints and Variables .................................................................................................................. 5 
3.1. 
Variables .................................................................................................................................. 5 
3.2. 
Endpoints ............................................................................................................................... 11 
3.2.1. Primary Endpoints ............................................................................................................... 11 
3.2.2. Secondary Endpoints ........................................................................................................... 11 
4. 
Statistical Methods ........................................................................................................................ 13 
4.1. 
Descriptive Statistics of Baseline Variables ........................................................................... 13 
4.2. 
Analysis of Primary Endpoints ............................................................................................... 13 
4.3. Analysis of Secondary Endpoints ............................................. Fehler! Textmarke nicht definiert. 
5. Treatment of Missing Values ............................................................................................................. 15 
6. Software ............................................................................................................................................ 15 
 
 
 

 
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1. Background of the Study 
The incidence of the olecranon fracture (OF) in adults is around 12 per 100,000 inhabitants per year.1 
The anatomical shape of the proximal ulna is largely responsible for the stabilization of the 
humeroulnar joint and reconstruction is therefore obligatory, but often challenging. Surgical treatment 
of the olecranon fracture is performed using tension band wiring (TBW) or locking plate fixation (LPF) 
osteosynthesis. It is not yet clear, which procedure is superior for a specific patient. In future, an 
individualized and objectified assessment of expected general and fracture-specific complications 
should enable the treatment to be individually adapted to the patient's risk profile. This shall prevent 
complications, unnecessary treatments, and treatment costs. In the project presented here, the reality 
of care for surgically treated patients with olecranon fractures will be analyzed using routine data 
collected by the BARMER health insurance fund. 
The aim of the study is to analyze differences in the outcome of patients with an olecranon fracture 
treated with TBW compared to LPF and to identify independent risk factors for unfavorable course.  
2. Population 
The German reimbursement system governs the remuneration of health care services subject to 
encoded diagnoses (International Statistical Classification of Diseases, German Modification; ICD-10 
GM) and procedures (German procedure classification – Operationen- und Prozedurenschluessel; OPS) 
by means of the ‘German Diagnosis Related Groups’ taxonomy (GDRG). This obligatory documentation 
and accounting system is specified and further regulated in detail by mandatory coding instructions. 
The database consists of retrospective health claims data of the German BARMER health insurance 
company. This includes anonymized data from following sectors: 
- 
Inpatient data (§301 SGB V): In addition to information on costs, duration of hospitalization 
and information about treating hospital, standardized information on diagnoses (coded 
according to ICD-10 GM) and procedures (coded according to OPS) are available. 
- 
Outpatient data (§295 SGB V): In addition to information on costs, diagnoses (ICD-10 GM) and 
procedures (OPS). 
- 
Pharmaceutical therapies (§300 SGB V): Information on medication (coded via ATC 
classification), as well as costs and DDD (Defined Daily Dose). 
All adult patients with an age of 18 years and older with an inpatient treated OF (ICD S52.01) treated 
with LPF or TBW between 01/2011 and 09/2023 will be included to the evaluations. Patients were 
grouped by age (i.e. 18-44 years, 45 – 69 years, ≥ 70 years). Younger patients (<70 years) and older 
patients (≥ 70 years) will be analyzed in separate studies.   
2.1. 
Treatment Groups 
The patient population will be divided into four treatment groups based on the first treatment 
received.  
 
Group 1: 
Locking Plate fixation for simple fractured OFs (sLPF) 
  
                     Patients allocated to this treatment group received a locking plate fixation       
 
 
after the first coded diagnosis of simple fractured OF.  
 

 
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Group 2: 
Locking Plate fixation for multi-fragmented OFs (LPF) 
   
                     Patients allocated to this treatment group received a locking plate fixation                             
after            after the first coded diagnosis of multi-fragmented OF. 
 
Group 3: 
Tension band wiring for simple fractured OFs (sTBW) 
 
                     Patients allocated to this treatment group received a tension band wiring fixation  
                     after the first coded diagnosis of simple fractured OF. 
 
Group 4: 
Tension band wiring for multi-fragmented OFs (TBW) 
  
              Patients allocated to this treatment group received a tension band wiring fixation  
                     after the first coded diagnosis of multi-fragmented OF. 
If TBW and LPF were coded at the same day and side, patients will be allocated to the LPF groups. 
2.2. 
Inclusion and Exclusion Criteria 
Within an index period from 01/2011 to 09/2023 all patients will be included, who met all inclusion 
criteria and no exclusion criterion (see table 1).  
Inclusion Criteria 
Inpatient coded diagnosis of olecranon fracture (ICD S52.01) 
Exclusion Criteria 
Incomplete basic information 
Incomplete insurance status within two years before index 
Previous treatment of olecranon fracture 
Unclear treatment of olecranon fracture (other as variable and code from table 2) 
Age < 18 years 
Coded polytrauma 
Bone tumors/ bone metastasis 
Both sides injured or missing information of surgery side  
Table 1: Inclusion and exclusion criteria.  
The first hospitalization within the index period with coded diagnosis for OF (S52.01 main and 
secondary diagnosis) and at least one coded surgical treatment using TBW (OPS 5-793.27, 5-794.17) or 
LPF (OPS 5-793.k7, 5-794.k7) will be defined as the index case. In addition, all overlapping cases 
without time delay (admission date new case = discharge cases with surgery) will be defined as one 
case-series and will be included in the index case. 
3. Endpoints and Variables 
3.1. 
Variables 
The following table lists all variables relevant to the analysis along with their ICD, OPS or ATC codes. 
For each patient, possible comorbidities will be recorded at baseline by including all outpatient and 
inpatient information coded within two years prior to the index hospitalization and during first 
hospitalization (exceptions are marked accordingly). 
The "minor outpatient complications" defined below (see the last row of the following table) will be 
based exclusively on outpatient information coded after discharge of the first hospitalization.  
All other variables concerning complications during follow-up will be collected exclusively from 
inpatient information during hospitalization and after discharge.  

 
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Variable 
Classification Code 
Olecranon fracture 
ICD 
S52.01 
Simple fracture TBW 
OPS 
5-793.27 
Multi-fragmented TBW 
OPS 
5-794.17 
Simple fracture LPF 
OPS 
5-793.k7 
Multi-fragmented LPF 
OPS 
5-794.k7 
Comorbidities at Baseline 
Alcohol abuses 
ICD 
E24.4, F10, G31.2, G62.1, G72.1, I42.6, K29.2, K70, K85.2, 
K86.0, T51.0, T51.9 
Arthrosis 
ICD 
M15-M19 (only before index admission) 
Atherosclerosis  
ICD 
I70 
Atrial fibrillation and flutter 
ICD 
I48 
Asthma 
 
J45 
Bone tumor/metastasis 
ICD 
C40.0, C79.5, C79.86, C79.9 
Cancer 
ICD 
C 
Chronic kidney disease 
ICD 
N18, N19 
Chronic polyarthritis 
ICD 
M05, M06 
Congestive heart failure  
ICD 
I50 
Coronary heart disease  
ICD 
I25 
Dementia 
ICD 
F00, F01, F02, F05.1, G30, G31.1 
Depressive episode 
ICD 
F32, F33 
Diabetes mellitus 
ICD 
E10-E14 
Dorsalgia 
ICD 
M54 
Hypertension  
ICD 
I10-I15 
Infection 
ICD 
M86.02, M86.12, M86.22, M86.32, M86.42, M86.52,  
M86.62, M86.82, M86.92, T84.5, T84.6, T84.7 (only before 
index admission) 
Neurotic, stress-related and 
somatoform disorders 
ICD 
F41, F43, F45 
Nicotine abuses 
ICD 
F17 
Obesity 
ICD 
E66 
Osteoporosis 
ICD 
M80-M85 
Parkinson 
ICD 
G20 
Polytrauma  
ICD, OPS, 
DRG 
ICD: T07, 
OPS: 5-982,  
or coded DRG started with “W” 
(only during index hospitalization) 
Elbow arthrosis 
ICD 
M25.52 (only before index admission) 
Previous stroke 
ICD 
I60-I69 (only before index admission) 
Prior level of care (LoC) 
 
Level of care in the database (from 2017) 
Problems related to care-
provider dependency 
ICD 
Z74 

 
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Pharmaceutical therapy 
 
 
Any anticoagulant 
ATC 
B01AA, B01AB, B01AC, B01AE, B01AF, B01AX 
Vitamin D or calcium 
ATC 
A11CC 
Bisphosphonates 
ATC 
M05BA, M05BB 
Any osteoporosis 
pharmacotherapy 
ATC 
Vitamin D/Calcium or Bisphosphonates 
Contraceptives for topical 
use 
ATC 
G02B (only for matching) 
Hormonal contraceptives for 
systemic use 
ATC 
G03A (only for matching) 
General Complications 
Acute liver failure 
ICD 
K72.0, K72.7, K72.9 
Acute myocardial infarction 
ICD 
I21, I22 
Acute renal failure 
ICD 
N17 
Acute respiratory distress 
syndrome 
ICD 
J80 
Cardiac arrest 
ICD 
I46 
Deep vein thrombosis 
ICD 
I80.1, I80.2, I82.2, I82.3 
Delirium 
ICD 
F05 
Pulmonary embolism 
ICD 
I26 
Sepsis 
ICD 
A41, A40, B37.7, R65.0, R65.1, R65.9, R57.2 
Stroke 
ICD 
I60-I64 
Ischemic stroke 
ICD  
I63-I64 
Resuscitation 
OPS 
8-77 (also defined as complication, if it happens on the same 
day as surgery) 
Intensive care 
OPS 
8-980, 8-98f (only during hospital stay) 
Blood transfusion 
OPS 
8-800.0, 8-800.1, 8-800.c (only during hospital stay) 
Surgical complications (at least one day after surgery) 
Conversion to TBW 
OPS 
5-793.27, 5-794.17 
Conversion to LPF 
OPS 
5-794.k7, 5-793.k7 
Endoprosthetic joint and 
bone replacement 
OPS 
5-824.40, 5-824.41, 5-824.50, 5-824.51, 5-824.52 
Conversion to other fracture 
fixation 
OPS 
5-790.07, 5-790.17, 5-790.27, 5-790.37, 5-790.47, 5-790.57, 
5-790.67, 5-790.97, 5-790.d7, 5-790.k7, 5-790.m7, 5-790.n7, 
5-790.p7, 5-790.x7, 5-793.17, 5-793.37, 5-793.67, 5-793.77, 
5-793.87, 5-793.97, 5-793.a7, 5-793.b7, 5-793.c7, 5-793.g7, 
5-793.h7, 5-793.m7, 5-793.n7, 5-793.x7, 5-794.07, 5-794.27, 
5-794.57, 5-794.67, 5-794.77, 5-794.87, 5-794.a7, 5-794.b7, 
5-794.c7, 5-794.g7, 5-794.m7, 5-794.n7, 5-794.x7 
Conversion, any 
OPS 
Any conversion as defined above  
Upper limb amputation, 
ipsilateral (exarticulation 
elbow or forearm) 
OPS 
5-862.2, 5-862.3, 5-862.4 
Bursitis  
ICD 
M70.2, M70.3 (only during hospital stay) 
Compartment syndrome 
ICD 
S51.86 (only during hospital stay) 

 
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Consequences of injury of 
the upper extremity 
ICD 
T92.1 (only during hospital stay) 
Haematoma after surgery 
ICD 
T81.0 (only during hospital stay) 
Implant dislocation 
ICD 
T84.11 (only during hospital stay) 
Mechanical malfunction or 
material failure/loosening 
ICD 
T85.88, T85.9 (only during hospital stay) 
Peri-prosthetic or peri-
implant fracture 
ICD 
M96.6, T84.11 (only during hospital stay) 
Surgical incidents 
ICD 
Y69, Y82.8, Y84.9 (only during hospital stay) 
Delayed union (if coded 
within six months) 
OPS 
5-781.a7, 5-782.17, 5-782.27, 5-782.37, 5-782.47, 5-782.57, 
5-782.a7, 5-782.b7, 5-782.x7, 5-784.07, 5-784.17, 5-784.27,  
5-784.37, 5-784.47, 5-784.77, 5-784.87, 5-784.b7, 5-784.c7,  
5-784.d7, 5-784.e7, 5-784.f7, 5-784.x7 
Infection 
ICD 
T84.5, T84.6, T84.7, M86.02, M86.12, M86.22, M86.32, 
M86.42, M86.52, M86.62, M86.82, M86.92 (only during 
hospital stay) 
OPS 
5-780.47, 5-780.57, 5-780.67, 5-780.77, 5-780.87, 5-780.97, 
5-785.17, 5-785.57, 5-785.77, 5-800.24, 5-800.25, 5-800.34, 
5-800.35, 5-800.a4, 5-800.a5, 5-800.b4, 5-800.b5, 5-810.14, 
5-810.15, 5-810.74, 5-810.75, 5-810.84, 5-810.85, 5-850.h2, 
5-850.j2, 5-892.37, 5-892.47, 5-896.27, 8-989, 8-989.0,  
8-989.1, 8-989.2, 8-989.3, 8-989.4, 8-989.5, 8-989.6 
Infection, resistant 
ICD 
U80-83 (only during hospital stay) 
OPS 
8-987 
Joint damage / cartilage 
damage  
OPS 
5-780.37, 5-784.57, 5-784.67, 5-800.84, 5-800.85, 5-810.44, 
5-810.45, 5-812.04, 5-812.05, 5-812.34, 5-812.35, 5-812.94, 
5-812.95, 5-812.a4, 5-812.a5, 5-812.e4, 5-812.e5, 5-812.f4,  
5-812.f5, 5-812.g4, 5-812.g5, 5-812.h4, 5-812.h5, 5-812.k4,  
5-812.k5, 5-812.m4, 5-812.m5 
Luxation 
OPS 
8-201.4, 8-201.5 (also including outpatient sector after 
discharge) 
Malunion  
OPS 
5-781.07, 5-781.17, 5-781.27, 5-781.37, 5-781.47, 5-781.57, 
5-781.67, 5-781.77, 5-781.87, 5-781.97 
Nerve injury 
OPS 
5-040.1, 5-040.2, 5-040.3, 5-041.1, 5-041.2, 5-041.3, 5-044.1,  
5-044.2, 5-044.3, 5-045.1, 5-045.2, 5-045.3, 5-046.1, 5-046.2,  
5-046.3, 5-047.1, 5-047.2, 5-047.3, 5-048.1, 5-048.2, 5-048.3,  
5-049.1, 5-049.2, 5-049.3, 5-04b.1, 5-04b.2, 5-04b.3, 5-050.1,  
5-050.2, 5-050.3, 5-051.1, 5-051.2, 5-051.3, 5-052.1, 5-052.2,  
5-052.3, 5-053.1, 5-053.2, 5-053.3, 5-054.1, 5-054.2, 5-054.3,  
5-055.1, 5-055.2, 5-055.3, 5-056.1, 5-056.2, 5-056.3, 5-057.1,  
5-057.2, 5-057.3 (only during hospital stay) 
Non-union / 
Pseudoarthrosis (if coded 
after six months) 
OPS 
5-781.a7, 5-782.17, 5-782.27, 5-782.37, 5-782.47, 5-782.57, 
5-782.a7, 5-782.b7, 5-784.07, 5-784.17, 5-784.27, 5-784.37, 
5-784.47, 5-784.77, 5-784.87, 5-784.b7 
Osteonecrosis 
ICD 
M87.22, M87.32, M87.82, M87.92 
Postoperative stiffness, 
Adhesive capsulitis, Frozen 
elbow 
OPS 
5-800.64, 5-800.65, 5-800.c4, 5-800.c5, 5-810.24, 5-810.25, 
5-810.94, 5-810.95 

 
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Vascular injury 
OPS 
5-388.12, 5-395.12, 5-397.12 (only during hospital stay) 
Secondary surgery, open 
(LPF and TBW) 
OPS 
5-780.07, 5-780.17, 5-780.27, 5-780.37, 5-780.67, 5-780.x7,  
5-782.17, 5-782.27, 5-782.37, 5-782.47, 5-782.57, 5-782.a7, 
5-784.07, 5-784.17, 5-784.27, 5-784.37, 5-784.47, 5-784.57, 
5-784.67, 5-784.77, 5-784.87, 5-784.a7, 5-784.b7, 5-785.07, 
5-785.17, 5-785.27, 5-785.37, 5-785.47, 5-785.57, 5-785.67, 
5-785.77, 5-789.b7, 5-789.c7, 5-794.07, 5-794.27, 5-794.57, 
5-794.67, 5-794.77, 5-794.87, 5-800.14, 5-800.15, 5-800.34, 
5-800.35, 5-800.44, 5-800.45, 5-800.54, 5-800.55, 5-800.74, 
5-800.75, 5-800.84, 5-800.85, 5-800.94, 5-800.95, 5-800.x4, 
5-800.x5, 5-801.04, 5-801.05, 5-801.34, 5-801.35, 5-801.44, 
5-801.45, 5-801.b4, 5-801.b5, 5-801.c4, 5-801.c5, 5-801.g4, 
5-801.g5, 5-801.h4, 5-801.h5, 5-801.k4, 5-801.k5, 5-801.m4, 
5-801.m5, 5-801.n4, 5-801.n5, 5-801.p4, 5-801.p5, 5-850.02, 
5-850.12, 5-850.22, 5-850.32, 5-850.42, 5-850.52, 5-850.62, 
5-850.72, 5-850.82, 5-850.92, 5-850.a2, 5-850.b2, 5-850.c2, 
5-850.d2, 5-850.e2, 5-850.f2, 5-850.g2, 5-850.h2, 5-850.j2,  
5-851.12, 5-851.22, 5-851.32, 5-851.42, 5-851.52, 5-851.62, 
5-851.72, 5-851.82, 5-851.92, 5-851.a2, 5-851.b2, 5-851.c2, 
5-851.d2, 5-852.02, 5-852.12, 5-852.22, 5-852.32, 5-852.42, 
5-852.52, 5-852.62, 5-852.72, 5-852.82, 5-852.92, 5-852.a2, 
5-852.b2, 5-852.c2, 5-852.d2, 5-852.h2, 5-852.j2, 5-853.02,  
5-853.12, 5-853.22, 5-853.32, 5-853.42, 5-853.52, 5-853.62, 
5-853.72, 5-853.82, 5-853.92, 5-853.x2, 5-855.02, 5-855.12, 
5-855.22, 5-855.32, 5-855.42, 5-855.52, 5-855.62, 5-855.72, 
5-855.82, 5-855.92, 5-855.a2, 5-855.b2, 5-859.02, 5-859.12, 
5-862.2, 5-862.3, 5-862.4, 5-892.07, 5-892.17, 5-892.27,  
5-892.37, 5-892.47, 5-896.07, 5-896.17, 5-896.27 
Secondary arthroscopy (LPF 
and TBW) 
OPS 
5-782.b7, 5-784.c7, 5-784.d7, 5-784.e7, 5-784.f7, 5-810.04, 
5-810.05, 5-810.14, 5-810.15, 5-810.24, 5-810.25, 5-810.44, 
5-810.45, 5-810.54, 5-810.55, 5-810.64, 5-810.65, 5-810.74,  
5-810.75, 5-810.84, 5-810.85, 5-810.94, 5-810.95, 5-810.x4, 
5-810.x5, 5-811.24, 5-811.25, 5-811.34, 5-811.35, 5-811.44, 
5-811.45, 5-811.x4, 5-811.x5, 5-812.04, 5-812.05, 5-812.34, 
5-812.35, 5-812.94, 5-812.95, 5-812.a4, 5-812.a5, 5-812.e4, 
5-812.e5, 5-812.f4, 5-812.f5, 5-812.g4, 5-812.g5, 5-812.h4,  
5-812.h5, 5-812.k4, 5-812.k5, 5-812.m4, 5-812.m5, 5-812.x4, 
5-812.x5, 5-819.04, 5-819.05, 5-819.14, 5-819.15, 5-819.x4, 
5-819.x5 
Implant removal (LPF) 
OPS 
5-787.07, 5-787.17, 5-787.37, 5-787.67, 5-787.77, 5-787.g7,  
5-787.k7, 5-810.34, 5-810.35 
Implant removal (TBW) 
OPS 
5-787.07, 5-787.17, 5-787.27, 5-787.67, 5-787.77, 5-787.g7,  
5-810.34, 5-810.35 
Revision of the 
osteosynthesis (LPF and 
TBW) 
OPS 
5-785.07, 5-785.17, 5-785.27, 5-785.37, 5-785.47, 5-785.57, 
5-785.67, 5-785.77, 5-789.37, 5-78a.07, 5-78a.17, 5-78a.27, 
5-78a.57, 5-78a.67, 5-78a.77, 5-78a.87, 5-78a.97, 5-78a.c7, 
5-78a.g7, 5-78a.k7, 5-78a.m7, 5-78a.n7, 5-78a.x7, 5-793.07, 
5-793.17, 5-793.27, 5-793.37, 5-793.67, 5-793.77, 5-793.87, 
5-793.97, 5-793.a7, 5-793.b7, 5-793.c7, 5-793.g7, 5-793.h7, 

 
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5-793.k7, 5-793.m7, 5-793.n7, 5-793.x7, 5-794.07, 5-794.17, 
5-794.27, 5-794.57, 5-794.67, 5-794.77, 5-794.87, 5-794.a7, 
5-794.b7, 5-794.c7, 5-794.g7, 5-794.h7, 5-794.k7, 5-794.m7, 
5-794.n7, 5-794.x7, 5-824.4, 5-824.5, 5-825.01, 5-825.4,  
5-825.a, 5-825.m 
Resection arthroplasty (for 
spacer placement) 
OPS 
5-829.4 
Secondary arthroplasty 
OPS 
5-824.4, 5-824.5 
Arthrolysis 
OPS 
5-800.64, 5-800.65, 5-810.24, 5-810.25, 5-810.94, 5-810.95 
Classification of complications and long-term endpoints/events 
Major adverse event 
 
resuscitation, cardiac arrest, myocardial infarction, stroke, 
acute renal failure, acute liver failure, acute respiratory 
distress syndrome, sepsis or death from any case 
Thromboembolic event 
 
Deep vein thrombosis, pulmonary embolism, ischemic stroke 
or death from any case 
Surgical complications 
 
 
Adhesive capsulitis, arthrolysis, debridement, frozen elbow, 
implant removal within first 3 months, infection, infection 
with antibiotic-resistant germs, joint damage/cartilage 
damage, luxation, delayed union, non-union/ 
pseudoarthrosis, malunion, nerve injury, vascular injury, 
osteonecrosis, postoperative stiffness, secondary 
arthroplasty, secondary arthroscopy, secondary surgery 
(open) including revision surgery, upper limb amputation 
Implant-associated 
complications (IAC) 
 
Impingement, bursitis, mechanical malfunction or material 
failure/loosening, periprosthetic or periimplant fracture 
Non-implant associated 
complications (non-IAC) 
 
Infection, infection with antibiotic-resistant germs, 
hematoma after surgery 
Minor outpatient 
complications (LPF and 
TBW) 1 
ICD 
G56.1, G56.2, G56.3, I80.80, I80.81, M00.02, M00.12, 
M00.22, M00.82, M00.92, M13.12, M13.82, M13.92, 
M19.12, M19.22, M19.82, M19.92, M24.02, M24.12, 
M24.22, M24.32, M24.42, M24.52, M24.62, M24.82, 
M24.92, M25.12, M25.22, M25.32, M25.42, M25.52, 
M25.62, M25.72, M25.82, M25.92, M61.02, M61.12, 
M61.22, M61.42, M61.52, M61.92, M62.02, M62.12, 
M62.22, M62.32, M62.42, M62.52, M62.62, M62.82, 
M62.92, M65.02, M65.12, M65.22, M65.82, M65.92, 
M84.02, M84.22, M84.32, M84.82, M84.92, M86.12, 
M86.22, M86.32, M86.42, M86.62, M86.82, M86.92, 
M87.22, M87.32, M87.82, M87.92, M89.52, M96.6,  
T79.60, T81.4, T84.01, T84.11, T84.5, T84.6, T84.7 
OPS 
All outpatient codes OPS for LPF or TBW coded collected 
above 
Table 2: Definition of all variables 
 
 
                                                          
1 Data collection exclusively based on outpatient information coded after discharge. 

 
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3.2. 
Endpoints 
The following two sub-chapters list the primary and secondary endpoints to be analyzed together 
with their definition. For more information, as well as underlying ICP, OPS and ATC codes, see 
Chapter 3.1. 
3.2.1. Primary Endpoints 
 
Variable  
Definition 
Revision  
- 
Time from surgery to revision defined above. 
Implant removal (only) 
- 
Time from surgery to implant removal 
- 
Within first 3 months after surgery, an implant 
removal will also considered as a surgical 
complication 
- 
No SC is allowed to occur within 3 months and 
on the same day 
Surgical complications (SC) 
- 
Time from surgery of OF to surgical 
complications, with death being considered as 
a competing risk event. 
In-hospital SC rate (IH-SC) 
- 
SC after surgery during index hospitalization 
(yes/no) 
In-hospital implant–associated complications 
(IH-IAC) 
- 
IAC after surgery during index hospitalization 
In-hospital 
non-implant 
associated 
complications (IH-non-IAC) 
- 
Non-IAC 
after 
surgery 
during 
index 
hospitalization 
Table 3: Primary endpoints 
 
3.2.2. Secondary Endpoints 
Overall survival (OS) 
- 
Time from surgery to death of any cause. 
- 
Death will be determined using the coded 
death as the reason for withdrawal in the 
BARMER database. In addition, all inpatient 
cases will be reviewed during follow-up, to 
determine whether death was reported as the 
reason for discharge. 
30-day mortality 
- 
Death from any cause within first day after 
surgery (yes/no) 
- 
All patients with shorter follow-up time are 
excluded 
Major adverse events (MAE) 
- 
Time from surgery to resuscitation, cardiac 
arrest, myocardial infarction, stroke, acute 
renal failure, acute liver failure, acute 
respiratory distress syndrome, sepsis or death 
from any case.  
In-hospital MAE rate (IH-MAE) 
- 
MAE during index hospitalization (yes/no) 

 
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Thromboembolic events or death (TE)  
- 
Time from surgery to a thromboembolic event 
or death of any cause. 
In-hospital TE rate (IH-TE) 
- 
TE during index hospitalization (yes/no) 
In-hospital death 
- 
Death during index hospitalization (yes/no) 
- 
Counted, when death was reported as the 
reason for discharge.  
Minor outpatient complications (MOC) 
- 
Time from discharge to minor outpatient 
complications, with death being considered as 
a competing risk event. 
Length of hospital stay (LOS) during index 
- 
Days of hospitalization (from admission to last 
discharge with index case series). 
Charges during index  
- 
Sum of charges of all cases of the index case 
series 
Treatment trends during study period 
- 
Distribution of treatment variants per year 
Table 4: Secondary Endpoints 
 
Figure 1: chronological scheme of the study including time ranges for complications 
3.3. 
Possible sources of bias due to variable definition 
In-hospital complications will be defined by the above reported codes that are coded in the same 
inpatient case as the surgery of OF (i.e. the index case series). For all OPS codes, the date has to be 
later in course of hospitalization than the surgery of OF (datum surgery with LPF/TBW < datum OPS 
code). ICD codes are all coded at the date of discharge and no chronological order within one case will 
be available. However, the defined complications are of such a serious nature that they always 
represent an unfavorable scenario from the patient's point of view, irrespective of the chronological 
course during hospitalization. It can also be assumed that, preoperatively, they did not represent a 
contraindication for surgery, if they were present before. Thus, it can be firstly assumed that 
complications predominantly occurred after surgery and, secondly, that any bias from (a few) events 
happens before surgery should be very low. In summary, all ICD codes for the above-mentioned 
complications that will be coded during the index case will be considered as in-hospital complications.  
For all SC, only OPS ipsilateral coded procedures will be considered as complications. For ICD codes, no 
laterality will be available and thus, SC during follow-up will be mostly defined on OPS codes. For 

 
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osteonecrosis, however, it is therefore possible to wrongly count contralateral events as a 
complication which might add some bias, but both groups will be effected in the same manner.  
4. Statistical Methods 
4.1. 
Descriptive Statistics of Baseline Variables and Treatment trends 
For descriptive analysis of treatment trends over time and baseline characteristics, the entire cohort 
will be used. For nominal and ordinal variables, the absolute and relative numbers will be calculated. 
All baseline parameter (see table 2 in chapter 3.1) will be reported for the entire cohort and grouped 
by treatment groups.  
Time trends in the treatment of olecranon fractures using TBW vs LPF over study time will be presented 
as absolute and relative frequencies per year and possible trend will be tested via two-sided Cochran-
Armitage trend test.  Subgroup analyses, i.e. female/male patients or grouped by age, will be 
performed, if the data will be sufficiently large. All calculated p-values for time trends will be only 
calculated to illustrate the results and are in no way of a confirmatory nature. Therefore, the p-values 
in this part should be interpreted with caution. 
4.2. 
Analysis of Primary and Secondary Endpoints 
To analyze differences in the treatment groups (TBW versus LPF), a 1:1 propensity score (PS) matching 
will be performed to guarantee sufficient balance between them. Each patient treated with TBW will 
be matched with a patients treated with LPF, based on age, sex, fracture complexity, year of treatment, 
all clinical relevant comorbidities and pharmaceutical therapy at index hospitalization (listed in table 2 
“Comorbidities at Baseline” and “Pharmaceutical therapy”). Analysis set will defined by all patients 
included in the matching.  
The balance will be evaluated using risk differences, z-differences and sum of squared z-differences 
(SSQZ) and will be reported for all variables before and after matching. The hyper-parameter (i.e. 
caliper with, distance for continuous variables, factors with exact matching) of the PS matching will be 
chosen in such way that the sum of squared z-differences (SSQZ) will be minimized around the number 
of variables included in the matching procedure (k), i.e. 
 𝑘2
⁄ ≤𝑆𝑆𝑄𝑍 ≈𝑘. 
Overlap between matching groups will be presented by the histogram of logit(ps). The dependency of 
the Matching partners and thus a stratified evaluation will not be considered.  
In-hospital complications and 30-days mortality  
All in-hospital endpoints as well as 30-day mortality are given by binary variables. Absolute and relative 
frequencies for both treatment group will be reported and differences between them will be tested 
via two-sided χ²-independence test. Moreover, a multivariable logistic regression model will be 
performed to adjust for patient’s risk profile. Odds ratio (OR) comparing TBW and LPF for all in-hospital 
complications and 30-day mortality will be illustrated using forest plots.  
30-day mortality will be defined as primary endpoint instead of in-hospital death to avoid bias due to 
differences in the LOS of both treatment groups. Absolute and relative frequencies for in-hospital 
death will be reported for the sake of completeness; however, p-values for possible differences will 
not be interpreted in a confirmatory manner. 

 
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Complications during follow-up 
The start of observation will be defined by the day of surgery. Median follow-up time will be 
determined for the entire analysis set using Kaplan Meier estimate (death as censored event). 
For OS, MAE and TE, the Kaplan-Meier estimator will be determined for both groups and plotted for 
the survival functions along with unadjusted 95% confidence intervals (95%CI). Furthermore, at 
different time points (1 month, 3 months, 1-5 years), the event rates (1- survival function) will be 
reported with 95%CI and the total number of observed events per group. For the comparison of 
groups, the Log rank test will be conducted. Multivariable Cox regression models will analyze the 
impact of baseline variables on the endpoints. The resulting hazard ratios (HRs) will be presented along 
with its unadjusted 95% confidence intervals and illustrated in forest plots. 
For SC and minor outpatient complications, death will be considered as a competing risk event. Hence, 
cumulative incidence function (CIF) determined by Aalen-Johansen estimate and sub-distributional 
hazards using Fine & Gray Cox models2 will be calculated. Groups will be compared with Gray’s test. 
All results were presented in an analog way explain above (plot of CIFs, reporting of CIF at different 
time points, forest plot for the HRs).  
Multiple comparison problem 
As mentioned above, patients were grouped by age (i.e. 18-44 years, 45 – 69 years, ≥ 70 years), where 
younger (<70 years) and older patients (≥ 70 years) will be analyzed (and published) in separate studies.  
To account for the multiple test problem in each study separately (<70 years and ≥ 70 years), all p-
values comparing treatment-effects determined from multivariable analysis of all primary endpoint 
will be jointly adjusted using Bonferroni-Holm method3 to control the family-wise error rate with 
respect to the multiple comparison problem. Adjusted p-values will be compared with the overall 
significance level of 5%.  
Time-dependent analysis 
Should the evaluation reveal an overlap of the survival curves approximated with Kaplan-Meier, we 
will further investigate these with a time-dependent survival analysis or landmark analysis with suitably 
chosen cut-off values. In addition, the time-dependent hazard ratio will be plotted in the form of a step 
function. All time-dependent analyses will be of an exploratory nature only. 
4.3. Sensitivity analysis 
As a sensitivity analysis, Cox regression analysis for OS, MAE, TE and SC as well as logistic regression 
analysis for 30-day mortality, IH-MAE, IH-TE and IH-SC will be also performed using the entire OF 
cohort with different weights: 
Approach 
Definition of weights 
 
Control (LPF) 
Treatment (TBW) 
 
Entire cohort with original data* 
1 
1 
 
Inverse Probability of Treatment 
Weighting (IPTW)4 
1
1 − 𝑝𝑠
 
 
1
𝑝𝑠
 
Balanced (or overlap) weighting5 
𝑝𝑠 
1 −𝑝𝑠 
 

 
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PS weighting6 
min (𝑝𝑠, 1 −𝑝𝑠)
1 −𝑝𝑠
 
min (𝑝𝑠, 1 −𝑝𝑠)
𝑝𝑠
 
 
Table 5: Weighting approaches for sensitivity analysis. *As a first analysis, regression analyses will be performed using the 
entire cohort without weights. 4,5,6 refer to the references. ps propensity score determined using logistic regression. 
5. Treatment of Missing Values 
Missing values or inconsistent data in sex, day of birth, exit date of database lead to exclusion from 
study. For all other variables, no missing data will occur in the study, since all variables will be defined 
by existing ICD/OPS or ATC codes. If no related code will be found, the according variable will be set to 
zero. Since the considered comorbidities are highly relevant for any imbursement, it is very unlikely 
that they are not coded in the database. However, there could be a bias by setting all the variables as 
known variables. 
6. Software 
All statistical analyses will be performed using SAS (SAS Enterprise Guide Version 8.3, SAS Institute 
Inc., Cary, NC, USA) and R version 4.2.1, R foundation, Vienna, Austria. 
References 
1. Lenz M., Wegmann K., Müller L. P. & Hackl, M. (2019). Nonoperative treatment of olecranon 
fractures in the elderly—A systematic review. Obere Extremität, 14(1), 48–52.  
2. Fine JP, Gray RJ. A proportional hazards model for the subdistribution of a competing risk. J 
Am Stat Assoc. 1999; 94:496–509. 
3. Holm, S. (1979). A Simple Sequentially Rejective Multiple Test Procedure. Scandinavian Journal 
of Statistics, 6(2), 65–70. 
4. Kuss O, Blettner M, Börgermann J. Propensity Score: an Alternative Method of Analyzing 
Treatment Effects. Dtsch Arztebl Int. 2016; 113:597-603. 
5. Li F, Morgan KL, Zaslavsky AM. Balancing Covariates via Propensity Score Weighting, Journal of 
the American Statistical Association. 2018; 113:390-400. 
6. Li L, Greene T. A weighting analogue to pair matching in propensity score analysis. Int J Biostat. 
2013; 9:215-234.