Johannes Erhardt

Clinical Results for Minimally Invasive Locked Plating of Proximal Humerus Fractures

Objectives: To describe the minimally invasive treatment of fractures of the proximal humerus using the Non-Contact-Bridging (NCB) plate. The system allows secondary locking of screws to the plate with a locking cap and polyaxial (30° radius) screw placement. Design: Prospective cohort study. Setting: University Level I trauma center. Patients: Fifty-four patients with unstable fractures of the proximal humerus. Intervention: Minimal anterolateral acromial approach to the proximal humerus, percutaneous fracture reduction, and minimally invasive application of the NCB plate. Main Outcome Measurements: Constant Score and radiologic follow-up (anteroposterior and transscapular). Visual Analog Scale for subjective evaluation of pain and function. Results: After 17 months, the average Constant Score was 66.8 points (87% of the age- and sex-related normal values). Implant-related complications (plate impingement, screw perforation into the glenohumeral joint, loosening of screws) occurred in nine cases (17%). The rate of avascular necrosis was low (5.5%) and no cases of nonunion were seen. Conclusions: The effectiveness of the NCB is similar to other published methods of treatment for fractures of the proximal humerus and potentially provides a less invasive option for this problem. Complication rates and functional outcome in this series are comparable to the literature. An important factor in this technique is the process of percutaneous fracture reduction. The NCB plate is suitable for both a minimally invasive technique or standard open reduction and internal fixation through a deltopectoral approach; the surgeon must decide which approach is best for each particular fracture pattern and should be comfortable with both techniques.

Second generation locked plating of proximal humerus fractures—A prospective multicentre observational study

Surgical treatment of most displaced proximal humerus fractures is challenging due to osteoporosis. Locking plates are intended to provide superior mechanical stability. In a prospective multicentre study 131 patients were treated with second generation locked plating (NCB-PH, Zimmer, Inc.). The open procedure (n = 78) was performed using a deltopectoral approach; the minimally invasive technique (n = 53) involved percutaneous reduction and an anterolateral deltoid split approach. Clinical and radiological follow-up was obtained. Improvement in function (ROM) was statistically significant. Fracture type (AO) had the most significant impact on the incidence of complications. The most frequent complications detected were intra-articular screw perforation (15%) and secondary displacement (8%). Complication rate and functional outcome of the NCB-PH are comparable to reports in the literature. Not all problems are likely to be solved by this new generation of implants, i.e. secondary dislocation still occurred in 8% of our patients.

The position and number of screws influence screw perforation of the humeral head in modern locking plates: A cadaver study

Objectives: Screw perforation of the humeral head in locking plate osteosynthesis occurs in up to 30% of cases. The current study compared different fixation possibilities (eg, number and position of screws) to reduce screw perforation in the humeral head. Methods: A humeral head fracture with a missing medial support was created in 30 fresh-frozen cadavers and fixed with a polyaxial locking plate (NCB PH; Zimmer, Warsaw, IN). The constructs were loaded with increasing force and the number of cycles until screw perforation was recorded. Four different fixation methods were tested: group 1 five screws with fixed angle, group 2 five screws in polyaxial position according to bone strength, group 3 three screws, and group 4 five screws with 1 as an inferomedial support screw. Results: More screws in the humeral head significantly increased the number of cycles before screw perforation. An inferomedial support screw further increased the number of cycles. Polyaxial screw placement compared with fixed-angle placement had no effect on the screw perforation phenomenon. Conclusions: We recommend to position an inferomedial support screw, and at least 5 screws in the head fragment, when using a locking plate in proximal humerus fractures with disrupted medial hinge.

The treatment of periprosthetic fractures with locking plates: effect of drill and screw type on cement mantles: a biomechanical analysis

IntroductionPeriprosthetic fractures after cemented hip replacement are a challenging problem to manage. Biomechanical studies have suggested the benefit of using locking screws for plate fixation, but there are concerns whether screws damage the cement mantle and promote crack propagation leading to construct failure.MethodIn this biomechanical study, different screw types were implanted into the cement mantle after pre-drilling holes of different sizes, in unicortical and bicortical configuration. The presence of cracks and the pull-out resistance of these screws were then evaluated.ResultsNo unicortical screw induced cracks. Screws with a shortened tip, smaller flutes and double threads were significantly better for pull-out resistance. Bicortical screws were associated with a risk of local cement mantle damage, but also with a significantly greater holding power. By increasing the drill diameter, the onset of cracks decreased, but so does the pull-out resistance.

The Anatomical Course of the Lateral Femoral Cutaneous Nerve with Special Attention to the Anterior Approach to the Hip Joint.

BACKGROUND Injury to the lateral femoral cutaneous nerve (LFCN) is a risk during the operative anterior approach to the hip joint. Although several anatomical studies have described the proximal course of the nerve in relation to the anterior superior iliac spine (ASIS) and the inguinal ligament, the distal course of the LFCN in the proximal aspect of the thigh has not been sufficiently studied. The aim of this cadaveric study was to examine the branching pattern of the nerve, with special consideration to the anterior approach to the hip joint. METHODS Twenty-eight cadaveric hemipelves from 18 donors (10 paired and 8 unpaired specimens) were dissected. The LFCN branches were localized proximal to the inguinal ligament and traced distally into the area of the proximal aspect of the thigh. Distribution patterns of the nerve with respect to its relationship to the ASIS and the internervous plane of the anterior approach to the hip joint were recorded. RESULTS We found 3 different branching patterns of the LFCN: sartorius-type (in 36% of the specimens), characterized by a dominant anterior nerve branch coursing along the lateral border of the sartorius muscle with no, or only a thin, posterior branch; posterior-type (in 32%), characterized by a strong posterior nerve branch; and fan-type (in 32%), characterized by multiple spreading nerve branches of equal thickness. In 50% of the specimens, the LFCN divided into ≥2 branches superior to the inguinal ligament. Sixty-two percent of the LFCN branches entered the proximal aspect of the thigh medial to the ASIS; 27%, above; and 11%, lateral to the ASIS. The LFCN consistently coursed within the deep layer of the subcutaneous fat tissue. CONCLUSIONS Injury to branches of the LFCN cannot be avoided in approximately one-third of surgical dissections that use the anterior approach to the hip joint. To protect the anterior branch of the LFCN, the skin incision should be as lateral as possible. The posterior branch of the LFCN is most vulnerable in the proximal aspect of the anterior approach to the hip joint, where it can be expected to course within the deep layer of the subcutaneous tissue.

How many radiographs are needed to detect angular stable head screw cut outs of the proximal humerus - A cadaver study

INTRODUCTION Cut out of locking head screws is the most common complication of locking plates in fracture fixation of the proximal humerus with potentially disastrous consequences. Aim of the study was to find the single best and combination of radiographic projections to reliably detect screw cut outs. MATERIALS AND METHODS The locking plate was fixed to six cadaveric proximal humeri. Six different radiographs were performed: anteriorposterior in internal (apIR), in neutral (ap0) and in 30° external rotation (apER); axial in 30° (ax30) and 60° (ax60) abduction and an outlet view. Each head screw (n=9) was sequentially exchanged to perforate the humeral head with the tip and all radiographs were repeated for each cut out. Randomized image reading by two blinded examiners for cut out was done for single projection and combinations. RESULTS Interrater agreement was 0.72-0.93. Best single projection was ax30 (sensitivity 76%) and the worst was the outlet view (sens. 17%). Standard combination of apIR/outlet reached a sens. of 54%. The best combination of two was: apER/ax30 (90% sens.), of three: apIR/apER/ax30 (96% sens.) and of four: apIR/ap0/apER/ax30 (100% sens.). CONCLUSION Standard radiographs (ap/outlet), especially in internal rotation, may miss nearly half of screw cut outs. Single best radiographic projection was an axial view with 30° abduction. To account for all cut outs and correct screw position a combination of four projections was needed. These simple and feasible intraoperative and postoperative radiographs help to detect screw perforations of the locking plate reliably. LEVEL OF EVIDENCE I (Study of Diagnostic Test).

The influence of local bone quality on fracture pattern in proximal humerus fractures

INTRODUCTION Bone mineral density and fracture morphology are widely discussed and relevant factors when considering the different treatment options for proximal humerus fractures. It was the aim of this study to investigate the influence of local bone quality on fracture patterns of the Neer classification as well as on fracture impaction angle in these injuries. MATERIALS AND METHODS All acute, isolated and non-pathological proximal humerus fractures admitted to our emergency department were included. The fractures were classified according to Neer and the humeral head impaction angle was measured. Local bone quality was assessed using the Deltoid Tuberosity Index (DTI). The distribution between DTI and fracture pattern was analysed. RESULTS 191 proximal humerus fractures were included (61 men, mean age 59 years; 130 women, mean age 69.5). 77 fractures (40%) were classified as one-part, 72 (38%) were two-part, 24 (13%) were three- and four-part and 18 (9%) were fracture dislocations. 30 fractures (16%) were varus impacted, whereas 45 fractures (24%) were classified as valgus impacted. The mean DTI was 1.48. Valgus impaction significantly correlated with good bone quality (DTI ≥ 1.4; p = 0.047) whereas no such statistical significance was found for the Neer fracture types. DISCUSSION We found that valgus impaction significantly depended on good bone quality. However, neither varus impaction nor any of the Neer fracture types correlated with bone quality. We conclude that the better bone quality of valgus impacted fractures may be a reason for their historically benign amenability to ORIF. On the other hand, good local bone quality does not prevent fracture comminution.

10-Year Survival of Acetabular Reinforcement Rings/Cages for Complex Hip Arthroplasty

Introduction : Acetabular reinforcement rings/ cages (AR) are commonly used for reconstruction of bone defects in complex hip arthroplasty. The aim of this study was to retrospectively investigate the 10-year survival rate of Ganz reinforcement rings and Burch-Schneider cages used in a single institution. Material and Methods : Between September 1999 and June 2002 all ARs, implanted in one institution, were identified. All patients had regular clinical and radiographic follow-up and were included in this study. Their prospectively collected clinical and radiographic data was retrospectively analyzed. In case of death before the 10-year follow-up examination, patient’s families or their general practitioner was contacted by telephone. The main outcome measures were survival of the ARs and kind of revision surgery. Results : The 10-year survival rate was 77.7%. At 10-year follow-up, 5/60 (8,3%) patients could not be located and had to be excluded therefore. 27/55 (49,1%) were dead, whereof 22 had no revision of the ARs before death (after a mean of 66 months; range: 0 - 123). Of the remaining 28/55 (50,9%) patients, 23 patients (24 ARs) had no revision of the ARs. Conclusion : Despite the high mortality rate of this study’s collective, ARs for complex primary or revision total hip arthroplasty provided predictable long term results. Level of Evidence : Clinical investigation.

Endovascular embolisation is a successful and safe treatment for post-operative arterial complications after total hip arthroplasty and revision surgery

PurposeArterial complications are rare but clinically critical during or following total hip arthroplasty (THA) surgery. They usually require secondary interventions, either through open or endovascular approaches. In a retrospective study, we analysed indications for, as well as success and safety of, endovascular embolisation for arterial complications after THA.MethodsWe reviewed all arterial complications that had occurred through THA surgery and been treated by endovascular embolisation. We analysed angiographic findings, endovascular treatment, location in relation to the surgical approach and success of the interventions.ResultsBetween 1997 and 2013 we performed 3,891 THAs at our hospital. We identified 14 patients with acute arterial complications treated by minimally invasive endovascular embolisation. Clinical findings included swelling of the ipsilateral leg, pain, prolonged wound bleeding, decreased haemoglobin and/or haemodynamic instability. Angiography revealed pseudoaneurysm in 11 patients, arteriovenous fistulas in two and extravasation of contrast media in one. Two patients showed no signs of acute bleeding. Twelve patients were treated, each with a single session of endovascular embolisation; in two additional patients, the haematoma was evacuated. No complications from the endovascular treatment were observed in this series.ConclusionEndovascular embolisation is a safe and successful minimally-invasive method to treat arterial injuries occurring through THA. Therefore, it should be considered as a first-line option of treatment for those injuries.

Osteolytic changes around biodegradable cement restrictors in hip surgery.

Background and purpose — Biodegradable cement restrictors are widely used in hip arthroplasty. Like others, we observed osteolytic reactions associated with a specific cement restrictor (SynPlug; made of PolyActive) and reviewed our patients. Patients and methods — We identified 703 patients with suitable radiographs from our database (2007 to 2012) who underwent cemented hip arthroplasty and received a SynPlug biodegradable cement restrictor. We reviewed all available radiographs to determine the incidence, severity, and progression of osteolysis. Mean postoperative follow-up was 1.8 (1–7) years Results — 1 year after implantation, the femoral cortex showed thinning by 12% in the anterior-posterior view and by 8% in the axial view. This had increased to 14% and 12%, respectively, at the latest available follow-up postoperatively (at a mean of 4 years). Cortical thinning of less than 10% was found in 37% of patients, but cortical thinning of 10–30% was found in 56% of patients. In the remaining 7%, a reduction of more than 30% of the original cortical thickness was observed. Interpretation — Osteolytic changes associated with the SynPlug biodegradable bone restrictors are inconsistent and highly variable. While some patients showed increased weakening of the femoral cortex with the potential risk of periprosthetic fracture, in others the degree of osteolysis only increased slightly or stabilized after 2 or more years. Any cortical bone loss after total hip replacement should be avoided, so the use of PolyActive biodegradable cement restrictors should be discontinued. Patients with a PolyActive cement restrictor in place should be followed up closely after surgery.